Clearing terminal screen[...]

When I type man foo, and exit the man (or less or nano or whatever), the terminal goes back to what it was before invoking the command. But when I do that under GNU screen, the previous program remains on the screen after I quit it, and scrolls up as I enter further commands, which is ugly. Is there a way to make it go away?

terminal ... ugly
Maybe you'd better get a Mac, OP.