Refuse to accept buns back (4)
I believe the answer is:
snub
'refuse' is the definition.
(thesaurus)
'buns back' is the wordplay.
'back' says the letters should be written backwards.
'buns' in reverse letter order is 'SNUB'.
'to accept' is the link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for snub that I've seen before include "Refuse to acknowledge" , "Blank" , "Insult by ignoring" , "Short and blunt - rebuff" , "unusually short" .)