Edit by mojo:
Now even easier! In the lobby type /clan close "clan name" with the "clan name" being your clan name ofc, then relog if necessary and your clan is gone.
1) Go to www.rawrgunz.com
2)Log in with your in game username and password
3)Once loged on, you will see the clan you're in on the usercp, beneath it there's a delete option
4)Click on delete
5)choose the correct char and clan
7)Your Clan is deleted
Obviously this is only possible if you're the clan leader.
This isn't that long btw, just seem long explaining.