主干是 the dog has made the floor dirty.you just cleaned是定语从句,对floor进行修饰,只不过floor在定语从句中充当宾语,所以可以省略. 补充完整就是 the dog has made the floor(which/that)you just cleand dirty.
我们先分析这个句子的成分 the dog是主语,has made 是谓语,the floor 是宾语,dirty 是补语, 即the dog has made the floor dirty,狗把地板弄脏了 那么you just cleaned 就是定语从句,谁的定语从句?很明显是the floor。宾语的定语从句中,先行词是物时,它的关系代词可以是which 或that ...