Concert blaster (3)
I believe the answer is:
amp
'concert blaster' 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 "Device making sound louder" , "A flow of one coulomb per second" , "Certain amount of power" , "Device to up the sound of an electric guitar (abbr)" , "Unit of electricity, in short" .)