Small pastry cooked later during races (7)
I believe the answer is:
tartlet
'small pastry' is the definition.
(I know that tartlet is a type of small pastry)
'cooked later during races' is the wordplay.
'cooked' indicates anagramming the letters (letters cooked into a new form).
'during' is an insertion indicator.
'races' becomes 'tt' (Isle of Man Tourist Trophy races).
'later' is an anagram of 'artle'.
'artle' going within 'tt' is 'TARTLET'.
(Other definitions for tartlet that I've seen before include "little sweet pastry" , "Small open pastry" , "Small filled pastry case" , "single pastry" , "pastry dish" .)