Unusually bad sign for corporation (7)
I believe the answer is:
abdomen
'for corporation' is the definition.
(I've seen this before)
'unusually bad sign' is the wordplay.
'unusually' is an anagram indicator.
'sign' becomes 'omen' (omen is a kind of sign).
'bad' is an anagram of 'abd'.
'abd'+'omen'='ABDOMEN'
(Other definitions for abdomen that I've seen before include "Bodily region" , "Ban demo (anag)" , "Central part of the body" , "A main part of the body" , "pot" .)