You don't do that - i.e. you don't use a single desktop that you need to clear. That's a Windows thing, where multiple desktops never worked right, and always n

You don't do that - i.e. you don't use a single desktop that you need to clear. That's a Windows thing, where multiple desktops never worked right, and always needed add-ons. You put an extra Gnome toolbar on your screen's right side, and you add a "Desktop-switcher" applet (I also like the "System monitor" applet there, and a couple other gewgaws). Then you keep a desktop for each work topic (web, docs, mail, whatever), and a clean one for the visitors ;-). All one click away, generally work flawlessly. But there's also a "Show desktop" applet, to add to your single-desktop toolbar, if you insist.