There was a small dust-up between the kids over a toy at the playground.

dust-up 是名词，由 dust（灰尘）和 up（向上）组成，字面意思是"扬起灰尘"，引申为"小规模的争吵或打斗"，通常指不太严重的冲突。这个表达比较口语化。