Top chap expecting traps (4)
I believe the answer is:
apex
'top' is the definition.
(I've seen this before)
'chap expecting traps' is the wordplay.
'traps' indicates the answer is hidden within the clue (the answer is 'trapped' somewhere in the clue).
'APEX' is hidden within 'chap expecting'.
(Other definitions for apex that I've seen before include "reasonable fare" , "high-point" , "white collar union" , "Cheap fare" , "Topmost point" .)