Food is something eaten with biscuits by penguin (8,6)
I believe the answer is:
macaroni cheese
'food' is the definition.
(I've seen this before)
'something eaten with biscuits by penguin' is the wordplay.
'something eaten with biscuits' becomes 'cheese' (biscuits are often eaten with cheese).
'by' is a charade indicator (letters next to each other).
'penguin' becomes 'macaroni' (macaroni is a type of penguin).
'cheese' after 'macaroni' is 'MACARONI CHEESE'.
'is' is the link.
(Other definitions for macaroni cheese that I've seen before include "Instead of this savoury" , "dish - with 29a" , "melted in dish" , "Savoury pasta dish" , "food" .)