Knocked back (7)
(Another definition for swigged that I've seen is " drunk".)
'knocked back' is the definition.
(to rebuff is to reject or knock back)
This is the entire clue.
(Other definitions for rebuffed that I've seen before include "Cold-shouldered" , "Snubbed, slighted" , "Rejected outright and bluntly" , "Rejected ungraciously" , "Abruptly rejected" .)