In that the toes of the feet were partly of iron and partly of clay, the latter stages of this kingdom will be partly strong and partly fragile.

Its legs were of iron; its feet were partly of iron and partly of clay. ¹ 

In that you were seeing feet and toes ¹  partly of wet clay ²  and partly of iron, so this will be a divided kingdom. Some of the strength of iron will be in it, for you saw iron mixed with wet clay. ³