Vegetable ship brought back (4)
I believe the answer is:
leek
'vegetable' is the definition.
(leek is a kind of vegetable)
'ship brought back' is the wordplay.
'ship' becomes 'keel' (literary term for a ship).
'brought back' says the letters should be written backwards.
'keel' in reverse letter order is 'LEEK'.
(Other definitions for leek that I've seen before include "Welsh national emblem" , "Onion's relative" , "Green and white vegetable" , "Staffordshire town?" , "Vegetable associated with Wales" .)