Scallion cousin (4)
I believe the answer is:
leek
'scallion cousin' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for leek that I've seen before include "Staffordshire town?" , "Plant (onion relative) eaten as a vegetable" , "Bulb" , "Vegetable related to the onion" , "Foodstuff" .)