Purpose: The purpose of this study was to construct a clear definition of the concept of clinical supervision among psychiatric mental health nurse practitioners (PMHNPs) in South Korea. Methods: The hybrid model was used to perform concept analysis on supervision. Results from both the theoretical review of 17 studies and a field study interviewing 12 PMHNPs were included in the final process. Results: The concept of supervision was found to have complex features and to consist of multi-dimensional meaning units, with 4 levels (including 11 attributes and 36 indicators). The dimensions and their 11 attributes are suggested as follows: 1) Learning dimension (intensive practice, clinical knowledge and skills, reflective practice), 2) professional support dimension (supervision function, evaluation and feedback, supervisory relationship, autonomy), 3) institutional dimension (supervision framework, policy of clinical supervision), and 4) consequential dimension (ensure the qualities of nursing care, professional development). Conclusion: Based on the results, supervision is defined as: “The provision of guidance and feedback on matters of personal, professional, and educational development in the context of a supervisee’s experience of providing safe and appropriate nursing care.” The findings in this study provide helpful insights for understanding supervision and practice development.