Initially some uncooked seafood's hidden in dish (5)
I believe the answer is:
sushi
'dish' is the definition.
(sushi is a kind of dish)
'initially some uncooked seafood's hidden in' is the wordplay.
'initially' suggests taking the first letters.
The initial letters of 'some uncooked seafoods hidden in' is 'SUSHI'.
(Other definitions for sushi that I've seen before include "Japanese food" , "rice dishes" , "Oriental food" , "Japanese cuisine" , "Cold rice dish, often with raw fish" .)