Rutabaga, for one (5)
I believe the answer is:
tuber
'rutabaga for one' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for tuber that I've seen before include "Fleshy underground part of plant" , "One goes underground" , "or still vegetating?" , "Thickened underground stem" , "Rhizome, as of potato" .)