Principal role for a live wire (4)
I believe the answer is:
lead
I believe this clue is a quadruple definition!!
'principal' is the first definition.
(synonyms)
'role' is the second definition.
(thesaurus)
'for' acts as a link.
'a live' is the third definition.
(I've seen this before)
'wire' is the fourth definition.
(lead is a kind of wire)
(Other definitions for lead that I've seen before include "Metal - van - important role" , "Actor playing the principal role" , "Soft, heavy metal" , ""bullets"" , "Precede into dale" .)