Richard,
I see 2 possible ways of doing this.
1.- If you want to do this for some but not all of the glossaries on your moodle site OR do not want to hack your moodle site's core files. Go to a glossary, select the kind of sort you want, let's say you want "by creation date, descending". In your browser's location window, locate the URL of your glosssary with those settings, something like:
http://yourmoodleiste/mod/glossary/view.php?id=5&sortkey=CREATION&sortorder=desc&mode=date
Then you can copy-paste that adress anywhere you like on your moodle site's course(s) (inside an HTML block, in a resource, etc.).
2.- If you want that default sort to be applied on all of your moodle site's glossaries AND are willing to hack your moodle core files, I can try to provide a solution.
Joseph
PS.- If more moodlers want this feature, it might be useful to suggest it as a glossary setting, along with the other existing settings. But I doubt it would be useful to many people.