Cheese's not left, it's brought back (7)
I believe the answer is:
stilton
'cheese's' is the definition.
(Stilton is an example)
'not left it's brought back' is the wordplay.
'left' becomes 'l' (common abbreviation).
'brought back' says the letters should be written in reverse.
'not'+'l'+'its'='notlits'
'notlits' reversed gives 'STILTON'.
(Other definitions for stilton that I've seen before include "Lost tin (anag)" , "19 cheese" , "Strong blue cheese" , "English blue cheese" , "Blue 4 across" .)