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 "This vegetable", "Green and white vegetable", "Welsh symbolic vegetable", "Vegetable emblem of Wales", "Emblem of Wales", "Edible plant, Welsh symbol", "Vegetable associated with Wales", "Foodstuff", "Vegetable related to onions" and "Staffordshire town?".)