Measure of current (3)
I believe the answer is:
amp
'measure of current' 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 "Current measure" , "Map of electric current" , "In short, unit for measuring electric current" , "Current; hi-fi kit" , "Unit of electricity, in short" .)