The point of chewing a bun (3)
I believe the answer is:
nub
'the point' is the definition.
(I've seen this before)
'chewing a bun' is the wordplay.
'chewing' indicates anagramming the letters.
'bun' anagrammed gives 'NUB'.
'of' acts as a link.
(Other definitions for nub that I've seen before include "Most essential part of an idea" , "Point or gist" , "'Gist, central idea (3)'" , "Centre point or core of a matter" , "Central core of bun" .)