Pub had some food — that's natural (6)
I believe the answer is:
innate
'natural' is the definition.
(I know that natural can be written as innate)
'pub had some food' is the wordplay.
'pub' becomes 'inn' (an inn is a type of pub).
'had some food' becomes 'ate' (to eat is to have food).
'inn'+'ate'='INNATE'
'that's' acts as a link.
(Other definitions for innate that I've seen before include "Inborn in neat way" , "native" , "Inherent or inborn" , "instinctive ..." , "Born" .)