Central point, gist (3)
I believe the answer is:
nub
I believe this is a double definition.
'central point' is the first definition.
(I've seen this in another clue)
'gist' is the second definition.
(synonyms)
(Other definitions for nub that I've seen before include "Most essential part of an idea" , "Metal piece" , "Crux (of a matter)" , "Central core of bun" , "'Gist, central idea (3)'" .)