Clipping mask not showing?

You are using the right tools - just need to tweak how you are using them. The clipping mask clips the layer it is on by ALL of the following children under the same parent. So I tend to create a new group then put the red cube and the following clipping object in that group. That stops the following layers getting involved in the clipping. I think what you are seeing is it is being clipped by the white box AND the brown square. That is because the brown square is a sibling after the clipping layer.

So, create a group, put the red cube in it with clipping on, then put a while cube in there as well after it. (I think you can hide it if you want to but a copy there - even when hidden I think it still clips.) This mistake you are making is only that you assume the clipping command uses the next layer only, instead of all following layers under the same parent.