The teacher asked Xiao Ming to re-draw the picture because some lines weren't clear enough.

re-draw 是由前缀 re-（表示"重新、再次"）和动词 draw（画）组成的复合动词，意思是"重新画"。 前缀 re- 加在动词前通常表示重复或再次进行某个动作。draw 是动词，意思是"画、绘制"。