Later, a few cooked crustacean (5,4)
I believe the answer is:
water flea
'crustacean' is the definition.
(water flea is a kind of crustacean)
'later a few cooked' is the wordplay.
'cooked' indicates anagramming the letters.
'later'+'a'+'few'='laterafew'
'laterafew' anagrammed gives 'WATER FLEA'.
(Other definitions for water flea that I've seen before include "Tiny crustacean" , "Common name for Daphnia" , "Tiny creature" .)