If possible, see if anyone in the clan is able to reach out to the leader outside of the game. Find out if they are able and willing to briefly return in order to leave the clan. If not, your only alternative will be to start a new clan if desired. T
ake note of your fellow clan members and communicate who will be leader and what the clan name will be so that it can be found quickly.
Since Clan Leaders must invest a hefty amount of gold to start a clan, we do not wish to intervene in case they decide to return. However, we can explore alternatives to this in the future if this becomes a significant issue.