Cases play part in dish (9)
I believe the answer is:
casserole
'dish' is the definition.
(I know that casserole is a type of dish)
'cases play part' is the wordplay.
'play' is an anagram indicator.
'part' becomes 'role' (eg a theatrical role).
'cases' anagrammed gives 'casse'.
'casse'+'role'='CASSEROLE'
'in' acts as a link.
(Other definitions for casserole that I've seen before include "(Food cooked in a) stewpot" , "Oven dish" , "Cook slowly" , "Kind of stew" , "meal" .)