As a greedy person, this shellfish may be eaten (6)
I believe the answer is:
quahog
'this shellfish may be eaten' is the definition.
(edible clam)
'as a greedy person' is the wordplay.
'as' becomes 'qua' (Latin word meaning 'in the role of', 'as').
'a greedy person' becomes 'hog' (informal term).
'qua'+'hog'='QUAHOG'
(Other definitions for quahog that I've seen before include "North American edible clam" , "Round clam" .)