Gangster rings causing bad luck (6)
I believe the answer is:
hoodoo
'bad luck' is the definition.
(type of jinx or bad luck)
'gangster rings' is the wordplay.
'gangster' becomes 'hood' (I've seen this in another clue).
'rings' becomes 'oo' (multiple circles).
'hood'+'oo'='HOODOO'
'causing' is the link.
(Other definitions for hoodoo that I've seen before include "Thing or person that brings bad luck" , "bringer of misfortune" , "Bad luck some people bring" , "Bringer of bad luck" , "Thing or person thought to bring bad luck" .)