Main part of pencil? (4)
I believe the answer is:
lead
This clue is a triple definition!
'main' is the first definition.
(thesaurus)
'part' is the second definition.
(thesaurus)
'of' acts as a link.
'pencil?' is the third definition.
(lead pencil is a kind of pencil)
(Other definitions for lead that I've seen before include "Go first" , "Short wire used as jumper - Pb" , "Starring role - kind of pencil" , "Wire - show the way" , "Chief performer" .)