How to create an area behind which elements will be hidden?

Question

Graphic arts

There is a group of elements where there is a background and elements on it, but some elements stick out outside the background.
How do I create something like a border or frame so that I don't clip the elements myself, but hide them behind a border or frame within my background?
The artboard option doesn't work because the group of elements is on a layer and I need to save several such groups with a background and elements on a layer with a transparent background.
The picture shows an example of how it is now (on the left) and how it should be (on the right)

Answer 1

Hello,
I need to make the dark background layer a mask.
upd: clipping mask