Sweetheart reverses car in disgust (6)
I believe the answer is:
revolt
'disgust' is the definition.
('revolt' can be a synonym of 'disgust')
'sweetheart reverses car' is the wordplay.
'sweetheart' becomes 'lover' (I've seen this before).
'reverses' says the letters should be written backwards.
'car' becomes 't'.
'lover' backwards is 'revol'.
'revol'+'t'='REVOLT'
'in' acts as a link.
(Other definitions for revolt that I've seen before include "Rise in rebellion" , "Rebel; rebellion" , "Rebel, rise up against" , "Rebel or disgust" , "Organized opposition to authority" .)