Be too sweet (4)
I believe the answer is:
cloy
'be too sweet' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for cloy that I've seen before include "Annoy through excessive sweetness" , "Be sickly sweet" , "Satiate to the point of disgust" , "Make weary through over-sentimentality" , "Sicken by excess sweetness" .)