Baked food made from pasta, mostly, with egg in (8)
I believe the answer is:
macaroon
'baked food' is the definition.
(type of biscuit)
'pasta mostly with egg in' is the wordplay.
'pasta' becomes 'macaroni' (macaroni is a kind of pasta).
'mostly' means to remove the last letter.
'with' indicates putting letters inside.
'egg in' becomes 'o' (an 'o' resembles an egg. I am not sure about the 'in' bit.).
'macaroni' with its last letter taken off is 'macaron'.
'macaron' enclosing 'o' is 'MACAROON'.
'made from' is the link.
(Other definitions for macaroon that I've seen before include "Coconut-topped biscuit" , "Something nutty to enjoy" , "Sweet biscuit made with ground almonds" , "Almond or coconut biscuit" , "Light biscuit" .)