Sicken with excessive sweetness (4)
I believe the answer is:
cloy
'sicken with excessive sweetness' 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 over-sentimentality" , "Cause distaste by being too sweet or rich" , "Be disgustingly rich" , "Sicken with excessive sweetness/richness" , "Sicken by glutting" .)