Shelter knight from vegetable (4)
I believe the answer is:
Here is my best explanation:
'vegetable' is the definition.
(leek is a kind of vegetable)
'shelter knight' is the subsidiary indication.
'shelter' becomes 'lee' (I've seen this before).
'knight' becomes 'k'.
'from' is the link.
(Other definitions for leek that I've seen before include "Vegetable emblem of Wales", "Vegetable - Welsh symbol", "Cylindrical vegetable", "Onion relative", "Plant; Welsh emblem", "Edible plant, Welsh symbol", "Bulb", "Vegetable related to onions", "Onion family vegetable" and "Emblem of Wales".)