Swear after chum creates a fuss (7)
I believe the answer is:
palaver
'a fuss' is the definition.
(I've seen this before)
'swear after chum' is the wordplay.
'swear' becomes 'aver' ('aver' can be a synonym of 'swear').
'after' says to put letters next to each other.
'chum' becomes 'pal' ('pal' can be a synonym of 'chum').
'aver' put after 'pal' is 'PALAVER'.
'creates' acts as a link.
(Other definitions for palaver that I've seen before include "Prolonged fuss" , "Idle copious talk" , "Song and dance" , "tedious bureaucracy" , "Time-consuming business" .)