Starchy root vegetable (4)
I believe the answer is:
taro
'starchy root vegetable' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for taro that I've seen before include "Starchy food" , "A rot turns the lily-like plant" , "Starchy plant" , "Fortune-telling cards" , "Chinese eddo" .)