Ena keeps youngster eating a Mexican dish (9)
I believe the answer is:
enchilada
'mexican dish' is the definition.
(enchilada is a type of Mexican dish)
'ena keeps youngster eating a' is the wordplay.
'keeps' means one lot of letters goes inside another.
'youngster' becomes 'child' (synonyms).
'eating' indicates putting letters inside.
'child' going around 'a' is 'chilad'.
'ena' placed around 'chilad' is 'ENCHILADA'.
(Other definitions for enchilada that I've seen before include "spicy dish" , "hot dish" , "wrap" , "Mexican dish" , "Rolled stuffed tortilla with chilli sauce" .)