Transparent Data Encryption (TDE)
If you use TDE to encrypt data at rest on the source database, DBCC CLONEDATABASE supports cloning of the source database but the cloned database is not encrypted by TDE. Thus, the backup of the cloned database will be unencrypted. If it is desired to encrypt and protect cloned database backup, you can enable TDE on cloned database before it is backed up as shown below
It’s a good read which covers several technologies.