Volt or ohm (4)
I believe the answer is:
unit
This clue is a double definition.
'volt' is the first definition.
(thesaurus)
'ohm' is the second definition.
(thesaurus)
(Other definitions for unit that I've seen before include "Individual thing; one" , "Item combining separate parts" , "Individual thing or group regarded as complete" , "Entity, system; component group" , "Operational team" .)