Bun spice (8)
I believe the answer is:
cinnamon
'bun spice' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for cinnamon that I've seen before include "Spice from dried bark" , "Spicy bark" , "spicy stuff" , "Aromatic tree bark used as a spice" , "Yellow-brown spice from bark of Asian tree" .)