Cheese dish (7)
I believe the answer is:
'cheese dish' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for rarebit that I've seen before include "cheesy meal" , "Toasted cheese and bread" , "Arbiter (anag) -- snack" , "Cheese on toast - arbiter (anag)" , "Arbiter of Welsh dish with melted cheese on toast" .)