Not innocent (6)
I believe the answer is:
guilty
'not innocent' is the definition.
('guilty' is the opposite to 'innocent')
This is all the clue.
(Other definitions for guilty that I've seen before include "Responsible for a crime" , "(Found) responsible for offence" , "Jury verdict - the accused did it" , "Blameworthy, at fault" , "Responsible for a reprehensible act" .)