Red vegetable (4)
I believe the answer is:
beet
'red vegetable' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for beet that I've seen before include "Root vegetable producing sugar" , "Genus of plant with succulent root" , "E.g. chard, mangelwurzel" , "Root used as a source of sugar" , "Sugar-yielding root" .)