Piece of band equipment (3)
I believe the answer is:
amp
'piece of band equipment' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for amp that I've seen before include "A flow of one coulomb per second" , "Unit of electricity, in short" , "It helps you hear" , "measure of power" , "Map about electric unit" .)