Plant used in making poi (4)
I believe the answer is:
taro
'plant used in making poi' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for taro that I've seen before include "A rot turns the lily-like plant" , "Root to eat" , "Fortune-telling cards" , "Starchy plant" , "Chinese eddo" .)