Roadie's load (3)
I believe the answer is:
amp
'roadie's load' 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 "Sound-boosting piece of equipment (abbr)" , "Map of electrical unit" , "Physics unit" , "It helps you hear" , "sound is increased by this" .)