One for the roadie (3)
I believe the answer is:
amp
'one for the roadie' 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" , "Device to up the sound of an electric guitar (abbr)" , "Unit of electric current - short version" , "Certain amount of power" , "sound is increased by this" .)