Hi,
Thank you for posting in Symantec community.
Could you please confirm whether you want to delete inactive clients or duplicate clients?
There is not any script to delete inactive clients, either delete them manually or SEPM will delete as per the settings.
To delete duplicate clients there is a script, refer these articles:
Repair duplicate IDs on cloned Endpoint Protection 12.1 clients
http://www.symantec.com/docs/TECH163349
How to prepare a Symantec Endpoint Protection 12.1.x client for cloning
http://www.symantec.com/docs/HOWTO54706