Be overly sweet (4)
I believe the answer is:
cloy
'be overly sweet' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for cloy that I've seen before include "Cause distaste by being too sweet or rich" , "Be sickeningly sweet" , "Gore as before" , "Nauseate" , "Annoy through excessive sweetness" .)