Lentil cousin (3)
I believe the answer is:
pea
'lentil cousin' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for pea that I've seen before include "Leguminous seed" , "Vegetable in a whistle" , "Legume" , "Ape this plant badly" , "Tiny stone" .)