Become overdone (4)
I believe the answer is:
cloy
'become overdone' 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 "Make weary through being overly sweet" , "Be sickeningly sweet" , "Satiate to the point of disgust" , "Be sickly sweet" , "Weary with excess" .)