I read the Dorsey's listed and this is the book for you. I scanned and did not find Clifford, but not all slaves are listed by name. They are in the wills, (listed), but only some by individual name.
I found the Dorsey book listed on a site where they reprint books no longer in print. You can order them soft back and hard back. This one is called.....
DORSEY and ALLIED FAMILIES..............by HIGGINSON BOOKS...........
I highly recommend them, I have purchased several things from them. I am not finding the site at this moment, but you can find it by search under their name.
Let me know if you are successful and I wish you Good Luck in your quest..........Best Regards..........Susan