Onion's kin (4)
I believe the answer is:
leek
'onion's kin' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for leek that I've seen before include "Onion's relative" , "English town" , "Bulb" , "Staffordshire town?" , "Eat the vegetable and keel over" .)