Electric guitar hookup (3)
I believe the answer is:
amp
'electric guitar hookup' 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 "Unit of electricity, in short" , "Map about electric unit" , "In short, unit for measuring electric current" , "A flow of one coulomb per second" , "Physics unit" .)