Cut out circular image from merged objects -- how?

Hello,

I have a portrait that's made up of several objects.

I want to turn it into a simple, round image:

So I basically want to place a circle above said objects and cut everything away outside that circle.

I've tried to do that in several ways:

For instance, I've placed a rectangle with a circular hole in it on top of the objects. I hoped it were possible to cut away the rectangle -- and everything beneath it -- and keep everything inside the circle. But I can't figure out how to do that. (I've tried the various functions in the Pathfinder.)

I also tried the other way around: Turning a circular shape into a Compound Path and placing it on top the objects. But to proceed from there and make a clipping mask, I also have to turn the objects below into Compound Paths -- but when I do that, all the colors disappear, and the colorless shapes that remain will be impossible to colorize again for various reasons.

So, is it impossible to make a simple round image from these objects?