Tosses the Maori king a crustacean (7)
I believe the answer is:
lobster
'a crustacean' is the definition.
(I know that lobster is a type of decapod)
'tosses the maori king' is the wordplay.
'tosses' becomes 'lobs' (I've seen this in another clue).
'the maori' becomes 'te' (I've seen this in other clues).
'king' becomes 'R' (abbreviation for rex, king in Latin).
'lobs'+'te'+'r'='LOBSTER'
(Other definitions for lobster that I've seen before include "One showing claws" , "Seafood" , "one for the pot?" , "Large edible crustacean" , "one to loft a > shellfish?" .)