Outlaw group sex (6)
I believe the answer is:
bandit
'outlaw' is the definition.
(I've seen this before)
'group sex' is the wordplay.
'group' becomes 'band' (band is a kind of group).
'sex' becomes 'it' (a common euphemism).
'band'+'it'='BANDIT'
(Other definitions for bandit that I've seen before include "Criminal type" , "Armed brigand" , "Member of a robber gang" , "hood" , "Outlaw, brigand" .)