Firstly you will need set server nameservers for addon domain at your domain registrar. DNS propagation will take 12-24 hours.
1. Log into your cPanel account.
2. In the “Domains” section, click on “Addon Domains” Icon.
click on “Addon Domains” Icon, In the “Domains” section
3. Beneath “Remove Aliases”, locate the parked domain name and click on the “Remove” link.
4. For confirmation, you will need to hit once again on the “Remove Alias” button.
You will be able to a message that your Parked/Alias Domain is removed successfully.