You can on the other hand go to NetVault Server > Media Management, double click the SD instance and you will then see your Clients that have used SD for the backup.
Then double click the Client and you will then see all the Savesets listed underneath.
Right click on the Saveset and select Remove and a warning pop-up window will appear to say that the Saveset will now be deleted and are you sure you want to delete it. Just click on OK and the Saveset will have now gone.
If you click on the refresh icon on the top left hand side, then if all the Savesets from that Client have been deleted, then the Client will disappear as well.
The Saveset is now gone from the NVDB and you can no longer perform a restore from that Saveset (even after re-scanning SD as well, so be careful what you want to remove).