is there a command to clear screen in SQLite3?

Depending on the shell. In Ubuntu -> .shell clear

On mac or Unix Operating systems:

   .shell clear

To execute CLS command in the SQLite3 shell you need to do this: .shell cls

As simple as that, .shell args... allows you to execute CMD commands in the SQLite3 shell.

There is no clear command in the SQLite command-line client.

But, if you're on a unix-based system (includes Mac OS X) you can use: Ctrl+L

Update:
While my answer is quick and simple, if you're on a compatible OS, make sure you also check out ivan0590's answer about the .shell command. Definitely a "good to know" as well.