Direct current is supplied by it (4)
I believe the answer is:
lead
This clue is a double definition.
'direct' is the first definition.
(synonyms)
'current is supplied by it' is the second definition.
(current might be supplied by a cable or lead)
(Other definitions for lead that I've seen before include "Guide, conduct" , "Command; metal" , "Go in front with heavy metal" , "1 down, symbol Pb" , "Go first" .)