Hello, i might be mistaken, but i think in the UNA system, there are various types of cache:

System cache - stores data about modules, templates, etc., Database cache - stores the results of queries, Page cache - stores rendered pages, CSS/JS cache - minified and combined files

A Cron job in UNA typically serves to perform scheduled tasks such as notifications, sending emails, updating statistics, and similar, but not necessarily for automatic cache clearing. @LeonidS would probably be able to answer this better and in more detail.