Not so sweet (5)
I believe the answer is:
drier
'not so sweet' is the definition.
('dry' can be the opposite of 'sweet' so perhaps 'drier' is reasonable for 'not so sweet')
This is all the clue.
(Other definitions for drier that I've seen before include "See 1" , "Machine giving spin" , "increasingly teetotal" , "It removes moisture" , "Flatter" .)