Bun to have when consuming most of a pop (7)
I believe the answer is:
teacake
'bun' is the definition.
(type of bun)
'have when consuming most of a pop' is the wordplay.
'have' becomes 'take' (taking is a kind of having).
'when consuming' indicates putting letters inside.
'most of' means to remove the last letter.
'a pop' becomes 'each' (eg 'one pound each' means 'one pound a pop').
'each' with its final letter taken away is 'eac'.
'take' placed around 'eac' is 'TEACAKE'.
'to' is the link.
(Other definitions for teacake that I've seen before include "Bun served toasted" , "bakery item" , "Fruited bun" , "Currant confection" , "Glazed bun, usually toasted and buttered" .)