A live wire, this conductor! (4)
I believe the answer is:
lead
I believe this is a triple definition!
'a live' is the first definition.
(I've seen this before)
'wire' is the second definition.
(lead is a kind of wire)
'this conductor' is the third definition.
(lead is a kind of conductor)
(Other definitions for lead that I've seen before include "Metal; show the way" , "Take the van with heavy metal" , "Metal - van - important role" , "Call the shots" , "Precede into dale" .)