Onion-like vegetable (4)
I believe the answer is:
leek
'onion-like vegetable' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for leek that I've seen before include "Foodstuff" , "Welsh national emblem" , "Vegetable emblem of Wales" , "One of the veggies" , "Plant related to the onion, pair with potato for soup" .)