Sugar source (4)
I believe the answer is:
cane
'sugar source' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for cane that I've seen before include "Bamboo rod" , "Beat - bamboo - stick" , "A light rod once used for punishment" , "Bamboo, sugar, stem" , "Birch" .)