Leave at the altar (4)
I believe the answer is:
jilt
'leave at the altar' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for jilt that I've seen before include "Reject a lover without warning" , "Discard abruptly" , "Be guilty of breach of promise" , "Spurn (lover)" , "Abruptly leave" .)