Not quite satisfied, having eaten nothing disgusting (4)
I believe the answer is:
foul
'disgusting' is the definition.
(both can mean horrible)
'not quite satisfied having eaten nothing' is the wordplay.
'not quite' means to remove the last letter.
'satisfied' becomes 'full'.
'having eaten' means one lot of letters goes inside another.
'nothing' becomes 'o' (looks like zero - 0).
'full' with its last letter removed is 'ful'.
'ful' placed around 'o' is 'FOUL'.
(Other definitions for foul that I've seen before include "Unfair, against rules of game" , "Abominable - offence on football field" , "Offensive to the senses" , "Putrid" , "Offensive; make dirty" .)