Object about argument, which is disconcerting (8)
I believe the answer is:
throwing
'disconcerting' is the definition.
(throwing is a kind of disconcerting)
'object about argument' is the wordplay.
'object' becomes 'thing' (an object is a thing or item).
'about' means one lot of letters goes inside another.
'argument' becomes 'row' (to row is to argue).
'thing' placed around 'row' is 'THROWING'.
'which is' is the link.
(Other definitions for throwing that I've seen before include "Puzzling" , "Projecting through the air" , "Chucking; unsettling" , "Propelling through the air" .)