Are you talking about the CICS application OR in ISPF?
If it is a Front End application that you want to issue clearscreen then it is PauseBreak( It's default settings ).
Other wise if it is ISPF there is no command to clear the screen as per myknowledge..
I have not work with TEs and hence not sure. Wouldn't this clearing thing be a bit application specific as such..because different main frame application may have different command for clearing all the things.