Criminal gang appeal (6)
I believe the answer is:
bandit
'criminal' is the definition.
(type of thief)
'gang appeal' is the wordplay.
'gang' becomes 'band' (both can mean a group of people).
'appeal' becomes 'it' ('it' can mean something attractive or appealing).
'band'+'it'='BANDIT'
(Other definitions for bandit that I've seen before include "Criminal type" , "Outlaw, brigand" , "Armed outlaw" , "(One-armed?) outlaw" , "Crook" .)