Well, how deep do you want to go with this? There is the straight forward issue of marketing the opening to TD and professional groups that are more diverse (any HBCU counseling programs in the area, any listservs in the state psych association dedicated to diversity, etc.).
Then there are the larger issues to deal with here, which is why do you have only white women at the clinic? The area, the pay, the atmosphere. etc.
Having been the "diversity" several during my career (read: the only employee that was not a white female and a different age), I am not sure I would take such a position if offered. I have often been the outgroup because being male and generally younger than many colleagues meant a lack of common interests and difficulty bonding with certain groups. Some were inclusive and some were a bit more tone deaf to including the minority (only talking about wedding/parent stuff, let't get mani/pedis after work ,etc). I don't know if I would take such a position or stay in it due to professional isolation. I have enjoyed the camraderie in more diverse workplaces much better. Something to keep in mind if you want to retain the person/persons.