Starchy vegetable (3)
I believe the answer is:
yam
'starchy vegetable' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for yam that I've seen before include "US sweet-potato" , "May be a foreign potato" , "Tropical tuber" , "Tuberous vegetable" , "May be a sweet potato" .)