Wickedly bad sign for belly (7)
I believe the answer is:
abdomen
'belly' is the definition.
(synonyms)
'wickedly bad sign' is the wordplay.
'wickedly' indicates an anagram (I've seen this in other clues).
'sign' becomes 'omen' (omen is a kind of sign).
'bad' anagrammed gives 'abd'.
'abd'+'omen'='ABDOMEN'
'for' acts as a link.
(Other definitions for abdomen that I've seen before include "Where one digests" , "Central region" , "pot" , "Ban demo (anag)" , "Part of body containing the stomach" .)