The map takes a little bit of time to update. Sometimes a few minutes, sometimes longer. You will probably also need a browser cache clear.

https://wiki.openstreetmap.org/wiki/Browser_cache

Clearcuts won't appear on the default map unless you combine it into a multipolygon with the forest, so that it's a "hole" in the forest. The reason is that there is no rendering on the default map for clearcuts, so these overlapping features just look like a forest. Other maps and programs may display it differently. A "hole" in the forest will simply not draw the forest there and leave it default white, so it becomes visible, so to speak.

Strictly speaking, you can't have both a forest and a clearcut at the same time. So these should normally be combined into multipolygons or drawn next to each other.

Multipolygons are a bit complicated. But you can select both areas (forest and clearcut) and press C to combine them. If the forest isn't a multipolygon yet, it will make one. If the forest is large and already has other parts outside the screen, you will have to download them first by selecting the forest relation and downloading its members. You can also manually add the cutline to the multipolygon relation without downloading other elements, but it's more annoying than just shift-selecting and C-ing them.

https://wiki.openstreetmap.org/wiki/Relation:multipolygon#iD