without appointing a new one (this just in case the old one has disappeared for ages or years, or hasn't done anything for the district during that time, or has expressed a wish step down; so use cautiously):

Go to the district page and add the following to the district page url:

&selectLeaderid=1

Like this: http://www.ancientworlds.net/aw/Places/District/hoodnumber&selectLeaderid=1

This results the name of the chief replaced by text/member name of "AncientWorlds Central";

After that you can ask around if someone else would like to take the lead, or even better; hold an election at the district, or best yet: a battle royal? And after the bloodshed you can appoint a new district leader.

PS: All this needs, of course, the editing powers of an AW Scribe, so don't try this at home... unless you are an AW Scribe, and at home.