Is there a way to install a fan switch for a ceiling fan that doesn't have a fan wire?
There are remote modules you can purchase to control the light/fan separately.  Most remote modules are wireless but there are some hardwired remote modules.  I've used both but my preference is to spend the 15 dollars more and get the hardwired control.  One that I've used and liked is this one from Lutron Maestro.  It will use the single hot wire to control both the fan and light using a control module you install at the base of the fan.