New equipment cases for band (4)
I believe the answer is:
ring
'for band' is the definition.
(a ring is a band of metal)
'new equipment cases' is the wordplay.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'equipment' becomes 'rig' (rig is a kind of equipment).
'cases' indicates putting letters inside.
'n' put within 'rig' is 'RING'.
(Other definitions for ring that I've seen before include "Contact" , "Phone; annulus" , "something at the jewellery shop?" , "sound as a bell" , "Call; circle" .)