Robber gang seizing equipment (7)
I believe the answer is:
brigand
'robber' is the definition.
(I've seen this before)
'gang seizing equipment' is the wordplay.
'gang' becomes 'band' (I've seen this before).
'seizing' indicates putting letters inside.
'equipment' becomes 'rig' (rig is a kind of equipment).
'band' going around 'rig' is 'BRIGAND'.
(Other definitions for brigand that I've seen before include "Marauder" , "Plunderer" , "Freebooter" , "Bandit" , "Robber in a gang" .)