Vegetable brought back in bottom of boat (4)
I believe the answer is:
keel
'bottom of boat' is the definition.
(I've seen this before)
'vegetable brought back' is the wordplay.
'vegetable' becomes 'leek' (leek is a kind of vegetable).
'brought back' shows that the letters should be reversed in order.
'leek' back-to-front is 'KEEL'.
'in' acts as a link.
(Other definitions for keel that I've seen before include "Coal-carrying vessel" , "Support on which ship is built" , "Long timber" , "Long base of a ship" , "Part of ship's frame" .)