Yeah, it really depends on the display interface ... if you want to clear an ANSI interface, you can use:
And that'll send a clear-screen command to the terminal. This works for me on PUTTY. Doesn't work on the PICAXE built-in serial monitor; for the PICAXE serial monitor you'll want to:
And then In "Settings" of your terminal, Special Control Code Functions, and select the "Clear Screen on FF [0C]" option. You *may* also want to ensure Settings > "Display non ASCII as HEX" is de-selected to make it look cleaner.