If you don't want your clients to see your website, you can Delete or Unpublish it.
How to delete a site
If you need to delete site with all pages, click Actions > Delete Site.
Sites are not deleted irreversibly, they are moved to Recycle bin first.
Deleted sites can be restored within 30 days. Then they are getting deleted irreversibly.
How to unpublish a site
If you don't want your clients to see your website but want to keep it, you can just Unpublish the website. Later you can publish this website again with the same address.