Valuable coin found in item of food (7)
I believe the answer is:
rarebit
'item of food' is the definition.
'valuable coin' is the wordplay.
'valuable' becomes 'rare'.
'coin' becomes 'bit' (I've seen this before).
'rare'+'bit'='RAREBIT'
'found in' is the link.
(Other definitions for rarebit that I've seen before include "cheesy meal" , "Cheese on toast - arbiter (anag)" , "Cheesy snack" , "Melted cheese with ale on toast" , "Welsh snack" .)