Just wanted to reply that I recently went through this same situation and currently there is no way to do this as of CPPM 6.8.3. If you need to send back multiple values for the same RADIUS attribute, which the A10 appliance wants in order to assign partition authorization via RADIUS, it wont work.
We were able to have ClearPass assign multiple enforcement profiles with the appropriate A10-Admin-Partition attributes, however it will only send back one of the attribute-value pairs in the RADIUS reply. While the CPPM roles and enforcement profiles were assigned appropriately, if you have multiple enforcement profiles sending back different values for the same attribute ClearPass will just overwrite the value and only send back one value for the attribute rather than stacking the values. Apparently there is no way to set the RADIUS reply to use a += value and stack the attributes as required by the A10.
More info from the A10 manual:
To authorize an administrator for access to multiple partitions, use the following RADIUS syntax:
A10-Admin-Partition = "partition-name1”
A10-Admin-Partition += " partition-name2”
A10-Admin-Partition += " partition-name3”
A10-Admin-Partition += " partition-name4”