Had a meal at back of pub, as is natural (6)
I believe the answer is:
innate
'is natural' is the definition.
(I've seen this before)
'had a meal at back of pub' is the wordplay.
'had a meal' becomes 'ate'.
'at back of' means one lot of letters go next to another.
'pub' becomes 'inn' (I've seen this before).
'ate' put after 'inn' is 'INNATE'.
'as' acts as a link.
(Other definitions for innate that I've seen before include "Inborn, natural to (6)" , "not needing to be taught" , "'Inborn, not learned (6)'" , "Congenital" , "Inherent or inborn" .)