Concert music blaster (3)
I believe the answer is:
amp
'concert music blaster' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for amp that I've seen before include "Device to up the sound of an electric guitar (abbr)" , "Certain amount of power" , "A flow of one coulomb per second" , "Physics unit" , "Sound booster" .)