Metal cable (4)
I believe the answer is:
lead
This clue is a double definition.
'metal' is the first definition.
(I know that lead is a type of metal)
'cable' is the second definition.
(thesaurus)
(Other definitions for lead that I've seen before include "Travel in front of" , "Go ahead; element" , "Guide; metallic element" , "Leash -- Pb" , "Soft, heavy metal" .)