Behaved disgustingly in minor quarrel (4)
I believe the answer is:
spat
I believe this clue is a double definition.
'behaved disgustingly' is the first definition.
(spat at someone)
'minor quarrel' is the second definition.
(I've seen this before)
'in' is the link.
(Other definitions for spat that I've seen before include "Contretemps" , "Unimportant quarrel between Pats" , "Taps in a small quarrel" , "Slight quarrel - ejected saliva" , "Minor conflict" .)