Existing literature suggests that a particular learning challenge for some doctoral candidates is coming to an understanding the concept of theory, that is the use of theory to frame research as well as theorising findings. The concept of theory has been identified as a Threshold Concept taking into account the characteristics of these concepts outlined by Meyer and Land. However, there has been little work that has focused on strategies that supervisors and candidates adopt to help them move from the liminal "stuck" space of not understanding, to crossing the conceptual threshold following insight and the "Aha!" moment. This paper draws on a Threshold Concepts framework, particularly liminality and being "stuck", in the analysis of interviews and discussions with 21 experienced supervisors and 10 doctoral candidates. It focuses on how participants witnessed and experienced "stuckness" regarding theory and theorising and strategies adopted to assist with understanding and becoming "unstuck".