Criminal -- for instance, gangster, bad at the outset (7)
I believe the answer is:
illegal
'criminal' is the definition.
('illegal' can be similar in meaning to 'criminal')
'for instance gangster bad at the outset' is the wordplay.
'for instance' becomes 'eg' ('e.g.' can be a synonym of 'for instance').
'gangster' becomes 'al' (Al Capone).
'bad' becomes 'ill' ('ill' can be similar in meaning to 'bad').
'at the outset' is a charade indicator (letters next to each other).
'eg'+'al'='egal'
'egal' put after 'ill' is 'ILLEGAL'.
(Other definitions for illegal that I've seen before include "Forbidden" , "Black-market" , "Contraband" , "Not in conformity with law" , "Not allowed" .)