Petty gangster or ruffian (7)
I believe the answer is:
hoodlum
This clue is a double definition.
'petty gangster' is the first definition.
(I've seen this before)
'ruffian' is the second definition.
(I've seen this before)
(Other definitions for hoodlum that I've seen before include "One breaks the law" , "tough!" , "Hooligan" , "Punk" , "American thug" .)