Currently, the default behavior of the "Copy Link" button on a Clip generates a public link. This means that if you share a public link, anyone with the link can view the video. However, they lack access to the transcript and comments of the Clip.
There should be a way of disabling public sharing of Clips, as there is generally for sharing views, tasks, Docs, etc. via public links. Clients don't want their content shared easily outside of the organization.