Usually CCleaner runs in a window, if you minimize the window it goes to the system tray where the icon flashes telling you that its doing its job. How about a setting where whenever CCleaner is activated, it runs directly from the system tray in the background, leaving screen space open for other, uninterrupted work.
You can create a shortcut.
I made mine by right clicking on the desktop > New > Shortcut.
Copy and Paste in location:
"C:\Program Files\CCleaner\CCleaner.exe" /AUTO
Name it CCleaner Auto.
CCleaner will run flashing in the tray.
/AUTO - Runs the cleaner upon loading and then closes the application.
I close my browser and all running apps. (excluding firewall, antivirus...) then I let CCleaner do its job before resuming any work.