Current measure a British politician provides (3)

I believe the answer is:
amp
'current measure' is the definition.
(short for ampere, unit of electrical current)
'a british politician provides' is the wordplay.
I cannot quite understand how this works, but
'a' is within the answer.
'politician' could be 'mp' (Member of Parliament) and 'mp' is found in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for amp that I've seen before include "A flow of one coulomb per second" , "Current; hi-fi kit" , "measure of power" , "Map of electric current" , "Current measure" .)
