CLOT stands for Custom Ladder Or Tournament. It is an extension to the game WarLight located at http://warlight.net. CLOT allows developers to host their own ladders or tournaments in any way they please.
For the official CLOT documentation, see http://wiki.warlight.net/index.php/CLOT
For a guide on how to get started making your own CLOT, see http://wiki.warlight.net/index.php/Getting_Started_with_CLOT