Argument as result of being oddly selective in formal clause (6)
I believe the answer is:
fracas
'argument' is the definition.
(I know that fracas is a type of dustup)
'being oddly selective in formal clause' is the wordplay.
'being oddly selective in' means one should take alternating letters (letters in odd-numbered positions are selected).
'formal'+'clause'='formalclause'
The alternating letters of 'formalclause' are 'FRACAS'.
'as result of' acts as a link.
(Other definitions for fracas that I've seen before include "Free-for-all" , "Scrap" , "A scarf (anag)" , "Brawl, disturbance" , "Fight" .)