Criminal group with sex appeal (6)
I believe the answer is:
bandit
'criminal' is the definition.
(type of thief)
'group with sex appeal' is the wordplay.
'group' becomes 'band' (band can mean a group of people).
'with' is a charade indicator (letters next to each other).
'sex appeal' becomes 'it'.
'band'+'it'='BANDIT'
(Other definitions for bandit that I've seen before include "Highwayman" , "Outlaw, brigand" , "Criminal type" , "Armed outlaw" , "Crook" .)