Had meal at back of pub? That's natural (6)
I believe the answer is:
innate
'natural' is the definition.
(similar in meaning)
'had meal at back of pub?' is the wordplay.
'had meal' becomes 'ate' (I've seen this in other clues).
'at back of' says to put letters next to each other.
'pub?' becomes 'inn' (I've seen this before).
'ate' after 'inn' is 'INNATE'.
'that's' acts as a link.
(Other definitions for innate that I've seen before include "'Inborn, not learned (6)'" , "Inherent, natural" , "Have tea in inn - it's natural" , "instinctive ..." , "Inborn in neat way" .)