Outlaw a musical group with it (6)
I believe the answer is:
bandit
'outlaw' is the definition.
(I know that bandit is a type of robber)
'a musical group with it' is the wordplay.
'a musical group' becomes 'band' (band is a kind of musical group).
'with' is a charade indicator (letters next to each other).
'band'+'it'='BANDIT'
(Other definitions for bandit that I've seen before include "Member of a gang of robbers" , "Armed robber in the Wild West" , "Violent robber" , "Marauder" , "Dan bit the robber badly" .)