If you are using Radiator and trying to configure TACACS on Clearpass for admin authentication, this configuration will help you - 
Put this in your ServerTACACSPLUS definition :


AuthorizeGroup admin permit service=cpass protocol=http {AdminPrivilege="Super Administrator"}
AuthorizeGroup admin permit service=cpass protocol=cli {AdminPrivilege="Super Administrator"}

The Clearpass documentation is here - 
https://community.arubanetworks.com/browse/articles/blogviewer?blogkey=72bcdff5-a399-426a-9fe6-4a866574162f