Petty squabble (4)
'petty squabble' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for spat that I've seen before include "Taps in a small quarrel" , "Showed contempt" , "Gestured with contempt" , "Reacted contemptuously" , "Made gesture of contempt" .)
(Other definitions for bicker that I've seen before include "Quarrel trivially" , "Quarrel pettily" , "Petty argument" , "Row" , "Clash" .)