Rhubarb as food (5)
I believe the answer is:
tripe
I believe this is a double definition.
'rhubarb' is the first definition.
(I've seen this before)
'food' is the second definition.
(tripe is a kind of food)
'as' is the link.
(Other definitions for tripe that I've seen before include "Balderdash" , "load of rubbish?" , "Ruminant's stomach lining" , "Junk; food" , "Rubbish (edible, maybe)" .)