You could also try using the Stealth activities so that the activity is hidden on the course page but still available to users. It's very simple and we use it all the time on content that we add on the front page.
Could I do something so that the link was be visible to admins, and teachers, but not students?
That’s expected behaviour as you’re “unpublishing” it and therefore it’s not available to students.
Where did you add the Glossary - the front page or within a course?
Depending on which version of Moodle you’re using, you may be able to use Stealth Activities - see https://docs.moodle.org/39/en/Stealth_activitiesThere may be other workarounds - but try Stealth first.
Thank you. The steal activities worked.