I suppose the quickest answer to this is yes, but it might involve a little scripting effort.
The version of Clearpass you have will dictate where options are and what they look like, but...
You can import users. Normally this is in XML format. Do an experimental export from your Clearpass to get the feel for it. With that format of the user information in mind, you just need a raw dump of the local user info from the controller to convert and macro/script.
On the local controller, I normally connect to the CLI, disable encryption ("encrypt disable"), then do a "show local-userdb". This will dump out the usernames and passwords, which you can copy across into an XML script or similar?
Thanks.