Mostly used-up pencil (3)
I believe the answer is:
nub
(Other definitions for nub that I've seen before include "Core, pith or gist" , "Centre point or core of a matter" , "Gist; small lump" , "Centre, heart" , "Gist - kernel" .)
I believe the answer is:
nub
(Other definitions for nub that I've seen before include "Core, pith or gist" , "Centre point or core of a matter" , "Gist; small lump" , "Centre, heart" , "Gist - kernel" .)