Cabbage genus (8)
I believe the answer is:
brassica
'cabbage genus' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for brassica that I've seen before include "Plant genus including many vegetables" , "Cabbages, cauliflowers etc" , "Plant of cabbage genus" , "Cabbage, say" , "Eg, cabbage, turnip, rape" .)