Bad luck as the gangster rings (6)
I believe the answer is:
hoodoo
'bad luck' is the definition.
(type of jinx or bad luck)
'the gangster rings' is the wordplay.
'the gangster' becomes 'hood' (I've seen this before).
'rings' becomes 'oo' (multiple circles).
'hood'+'oo'='HOODOO'
'as' acts as a link.
(Other definitions for hoodoo that I've seen before include "bringer of misfortune" , "Bad luck some people bring" , "Bringer of bad luck" , "Fetish - charm with magical powers" , "Jinx" .)