Previous research has shown that the use of clicker questions and Peer Instruction in a lecture can have a positive impact on students' understanding, especially their conceptual understanding. The quality of students' discussions plays a crucial role for increasing the understanding. However, little is known about the role that clicker questions play in triggering high quality collaborative discussions in undergraduate analysis courses. In this case study, I will show how a clicker question, designed to help understand AE and EA expressions, triggered the meaning making process of one group. Different interpretations of the expression were an ideal trigger to a high quality discussion. At the end I set up some hypotheses about the design of good clicker questions.