Upset sweets got over (8)
I believe the answer is:
stressed
'upset' is the definition.
'sweets got over' is the wordplay.
'sweets' becomes 'desserts' ('dessert' can be a synonym of 'sweet').
'got over' says the letters should be written backwards.
'desserts' backwards is 'STRESSED'.
(Other definitions for stressed that I've seen before include "Subjected to strain or emphasised." , "Physically or mentally overexerted" , "Suffering mental strain" , "Flustery" , "under force" .)