Essential bag for Spooner's bun (7)
I believe the answer is:
teacake
'bun' is the definition.
(type of bun)
I don't understand how the remainder of the clue works.
(Other definitions for teacake that I've seen before include "snack" , "(Afternoon) bun" , "Fruited bun" , "Sweet thing" , "crumbs from this?" .)