7'' display and screensaver

Hello,
I have an LCD Display that shows a clock when it’s not playing. It works like a charm.
Now I bought a 7’’ touch-display connecting via HDMI+USB to a pi zero. It also works like a charm, but I would like to show a clock when now playing. I tried different thinks, like installing xscreensaver and the like.
Can you help me? I can’t find anything useful.

Thanks
david