This study analyses teacher-led clarification sequences in a university second language classroom setting from a conversation-analytic perspective. In the literature, there are many studies of clarification requests, but the focus is on individual categories and quantification. No previous study has examined clarification, as reconceptualised in this study, as a social action using Conversation Analysis methodology. The study draws on 14 hours of L2 classroom data from Newcastle University Corpus of Academic Spoken English database involving international students studying English as a second language. The data is analysed using Conversation Analysis by specifically focusing on sequential organization and the repair mechanism. The findings offer a qualitative and detailed account of clarification from an emic perspective. The analysis suggests that teachers use three types of initiation in clarification and the selection of these types is shown to be strongly related to the extent of epistemic gaps. The analysis also shows that teachers use two further resources when students fail to clarify. These findings have implications for the organization of the repair mechanism in L2 classrooms and for training L2 teachers.