If your ban wasn't permanent you can always wait your ban out and either;
1. Assign a friend to Lieutenant and contact Z8games after a period of time to assign the clan to him.
2 You may contact Z8games support to delete your clan as well.
If you are asking this because your account was permanently banned, after a certain amount of time I believe your clan will automatically go to the person with the most clan points earned.
The time frame is 60 days;
"Please note that if a leader has not logged in to the game after 60 days they could be subject to Leadership Transfer to the top ranked lieutenant or member of their clan."
Top ranked is the most clan points. They will have to contact Z8games here;