I thought about adding a glossary to my thesis, but in the end I decided not to, as I thought it would "eat" a good part of my word count. Then, after the viva I had to clarify the meaning of some words in footnotes. So retrospectively it would have been better to insert the glossary.
I don't think you should reference what you write in the glossary, unless you write it in the style of a dictionary entry, and at that point you can reference things in-text using the author-date system.