Cooked crepes, one is filling for definite (7)
I believe the answer is:
precise
'definite' is the definition.
('precise' can be a synonym of 'definite')
'cooked crepes one is filling' is the wordplay.
'cooked' indicates anagramming the letters.
'one' becomes 'i' (Roman numeral).
'is filling' means one lot of letters goes inside another.
'crepes' anagrammed gives 'precse'.
'precse' going around 'i' is 'PRECISE'.
'for' is the link.
(Other definitions for precise that I've seen before include "Recipes (anag.)" , "Express" , "Detailed, exact" , "with accuracy" , "'Exact, accurate (7)'" .)