sing for your supper idiom old-fashioned
为晚餐而唱（为某人做某事，以取得某物作回报，特别是食物）
to do something for someone else in order to receive something in return, especially food
Dan's upstairs fixing my computer - I'm making him sing for his supper. 丹在楼上修理我的电脑－－修好后我请他吃饭。