He's not alone in breaking the law (8)
I believe the answer is:
gangster
'he's not alone in breaking the law' is the definition.
(someone who works with a gang to commit crimes)
This is the entire clue.
(Other definitions for gangster that I've seen before include "Hood, desperado" , "Member of criminal group" , "One of the mob, like Al Capone" , "One of a group of violent criminals" , "Crook" .)