Shelter given to base of weak vegetable (4)
I believe the answer is:
leek
'vegetable' is the definition.
(I know that leek is a type of vegetable)
'shelter given to base of weak' is the wordplay.
'shelter' becomes 'lee' (as in lee side, the side sheltered from wind).
'given to' means one lot of letters go next to another.
'base of' indicates one should take the final letters.
The final letter of 'weak' is 'k'.
'lee'+'k'='LEEK'
(Other definitions for leek that I've seen before include "what Fluellen wore in France?" , "Vegetable - Welsh emblem" , "Foodstuff" , "Vegetable related to the onion" , "Welsh symbolic vegetable" .)