Finally removed futon stain from vegetarian food (4)
I believe the answer is:
tofu
'food' is the definition.
(tofu is a kind of food)
'finally removed futon stain from vegetarian' is the wordplay.
I cannot really see how this works, but
'from' could be 'of' (of can mean from or belonging to) and 'of' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for tofu that I've seen before include "Food from bean curd" , "Substitute for meat" , "Form of curd" , "Soya bean dish" , "Unfermented soya bean curd" .)