According to the Norwegian White Paper No. 16 (2016-17) “Culture for Quality in Higher Education” [1] , the overall goal of nursing education is to produce reflective practitioners. Educating nurse specialist students (NSS) who possess these capabilities is complex. Reflection and reflective practice in nurse specialist education are considered essential for specialized professional competence. The students should be able to act and think professionally, integrating theory and practice from the outset. Reflective practice was increasingly focused upon in the literature from the 1990s [2] . According to Atkins [3] and Duffy [4] , reflective practice is defined as a learning and development process that includes self- examination of one’s professional practice, experiences, thoughts, emotions, actions and gaining knowledge that can enrich it. Clinical practice is a crucial part of the postgraduate education of NSS in Norway, comprising 50% of the education.

The focus of this study is the final part of the NSS’ postgraduate education in anaesthesia, intensive care, surgical and oncology nursing at the University College in June 2015. Specialist nursing practice entails encountering people in vulnerable and exposed situations. Specialist nurses have to function in complex health care systems, continuously refresh and update their skills and knowledge, in addition to framing and solving complex patient and healthcare problems [5] . At the same time, their work has become significantly more complex and they are under pressure to be efficient, making patient safety (PS) a hot topic. In Norway, most clinical nurse supervisors have no formal qualifications or training for supervision. However, the supervisors’ skills are significant for the quality of supervision and they are in a unique position to facilitate learning processes and promote the students’ professional growth and identity building as specialist nurses [6] . To enhance the students’ professional development, a systematic structure can lead to positive outcomes in terms of quality and PS [7] .

Healthcare delivery today comprises many benefits and challenges. Clinical supervision (CS) is one of the keys to maintaining and improving the overall quality of care, the professional development of personnel as well as patient and staff retention [8] .

CS is increasingly recognized as a vital part of effective, modern healthcare systems [9] . There are several definitions of CS in the literature. Proctor [10] includes three elements in his definition of the supervision process: formative, which means development, normative, which implies a standard setting and restorative, which indicates the provision of support. According to Severinsson [11] , three main concepts should be established in nursing supervision: confirmation, meaning and self-awareness. The general target of clinical supervision is to support the development of the supervisee’s job identity, competence, skills and ethics. The purpose of CS is to improve the quality of the nurse-patient relationship in terms of identifying and fulfilling a patient’s care needs in order to achieve a positive change that can be observed and measured. In such a process, the supervisee together with a more experienced practitioner can reflect on practice using case material in order to learn and refine skills [12] . In this paper, we adopted the definition from Bishop’s study, as it explains the importance of reflection and the fact that the focus of CS should be to ensure a safe and supportive environment that promotes the delivery of quality of care: “Clinical supervision is a designed interaction between two or more practitioners within a safe and supportive environment, that enables a continuum of reflective critical analysis of care to ensure quality patient services, and the well-being of the practitioner” [13] (p. 113).

Bishop’s study highlights reflection as a skill and a core area of CS. A search of the literature revealed that while there are many articles on the subject of reflection, few studies have linked it with NSS. Carroll et al. [14] claim that there is no clear definition of reflection or reflective practice and that the plethora of terms used interchangeably in the literature make the phenomenon difficult to utilize within nursing education. However, the present study first demonstrates that reflection leads to a new understanding and the intention to act differently in the future (an iterative dimension). Secondly, it shows different levels of reflection on experience. In general, the surface level is more descriptive and less analytical than the deeper level, which appears more difficult to reach. Dewey [15] focused on the depth and quality of reflective thinking, which is termed a vertical dimension. Dubé and Ducharme [2] also refer to the definitions of Boud et al. [16] , Dewey [15] , Mezirow [17] , Reid [18] and Schön [19] . Dubé and Ducharme [2] found that in all the studies the definitions of reflective practice identified the experience as the basis for new learning. In most studies, the process refers to Schön’s [19] reflection-in-action which means reflection during a clinical experience and reflection-on-action in the sense of reflection on a clinical experience after the fact. The work of Mezirow [17] indicates that the reflection process can operate at various levels of intensity: habitual action, thoughtful action, reflection or critical reflection. Studies by Callister et al. [20] , Cooper et al. [21] , Honey et al. [22] and Glaze [23] show that student nurses managed to develop reflective skills such as self-awareness, openness to others and their practices by following reflective practice in an academic context, as well as the various emotions experienced in a learning context, such as fear or anxiety.

NSS are educated and trained to work in high-tech departments with a strong focus on PS. Nowadays PS is increasingly recognized as a key dimension of quality care and has been integrated into the education of healthcare professionals [24] . Jha et al. [25] claim that despite the traditional principle of “do no harm”, unsafe medical care seems to cause significant morbidity and mortality all over the world. In particular, surgery and anaesthesia present substantial safety risks. In the US, estimates suggest that surgical adverse events account for 48% of all adverse events. The relevance of PS has expanded internationally [26] . With the complexity of today’s healthcare system, the successful treatment and outcome of each patient depend upon a range of factors. Many different types of healthcare professional are involved and it is difficult to ensure safe care unless the system is designed to facilitate timely and complete information and understanding by all. Accordingly, numerous factors such as understaffing and inadequate structures contribute to unsafe patient care [27] . The strategy includes the specific goal of improving PS and the quality of the healthcare services. The main dimension in PS and safety culture domains is respectful communication, which implies sharing experiences. Furthermore, the most important dimensions in the multidisciplinary capacity building domain are collaboration and teamwork, coordination and risk management, knowledge sharing and patient- centred communication [26] .

The study has a qualitative design [28] . In 2015, we conducted a quantitative survey that included qualitative questions focusing on how NSS experienced CS from their supervisors in relation to PS [29] . These qualitative questions constitute the empirical material in this study.

The study included all the 56 nurse specialist students (NSS) from four healthcare contexts in the final phase of their postgraduate education at the University College in June 2015 and eligible to participate in the study. In total, 46 NSS (8 anaesthesia, 11 intensive care, 14 operation/surgical and 13 oncological care) completed and returned the anonymous questionnaire to the first and the second author. The response rate was 81%.

The open questions focused on experiences of CS and competencies in order to ensuring PS: a) In CS I am particularly pleased with … b) In CS I would prefer changes to… c) How do you understand the concept of PS? d) Do you have the right competence to ensure PS? e) How can CS be important for PS? The characteristics of the participants are presented in Table 1.

In order to analyse the questions we applied Graneheim and Lundman’s [30] qualitative content analysis, a method for analysing written or verbal communication in a systematic way. A common component of qualitative interpretive content analysis methods is coding operations that translate one set of meanings into the other. The method presented by Graneheim and Lundman [30] consists