Units of electrical current (4)
I believe the answer is:
amps
'units of electrical current' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for amps that I've seen before include "Spam (anag)" , "concert gear" , "Basic units of electric current" , "'Units of electric current, in short (4)'" , "Current measures" .)