Substitute crepe filling with something dainty (7)
I believe the answer is:
replace
'substitute' is the definition.
(I know that substitute can be written as replace)
'crepe filling with something dainty' is the wordplay.
'filling' says to take the centre (the letters which fill the word).
'with' is a charade indicator (letters next to each other).
'something dainty' becomes 'lace' (lace is a dainty material).
The centre of 'crepe' is 'rep'.
'rep'+'lace'='REPLACE'
(Other definitions for replace that I've seen before include "Put something back where it belongs" , "Substitute, supersede" , "Substitute for (someone)" , "Put back in original position" , "Provide a substitute for" .)