Vehicle put in reverse, creating argument (4-2)
I believe the answer is:
bust-up
'argument' is the definition.
(a bust-up is an argument or quarrel)
'vehicle put in reverse' is the wordplay.
'vehicle' becomes 'bus' (public transport vehicle).
'in reverse' says the letters should be written backwards.
'put' backwards is 'tup'.
'bus'+'tup'='BUST-UP'
'creating' acts as a link.
(Other definitions for bust-up that I've seen before include "Quarrel, possibly ending a friendship" , "Serious altercation" , "Argument finishing a relationship" , "Quarrel, brawl" , "disagreement" .)