VERY high Core Audio CPU usage ALL the time? 2018 Mini

I see you are running CCleaner. You should uninstall CCleaner by following the developer's instructions. Do the same with any other anti-virus, cleaning/optimizer apps, and third party security software since none of them are needed on a Mac. These types of apps usually cause more problems than they solve, plus they impact system performance. Plus the less software running on your system, especially tied to the lower levels of the OS like these types of apps do, the better it will perform.

Effective defenses against malware and other threats - Apple Community

Plus CCleaner is now owned by another company (Avast which makes a formerly respected anit-virus app), so any possible good reviews & intentions CCleaner once had no longer apply. CCleaner has been bundled with unwanted extra applications without notice to the user, and CCleaner at one time shipped with a Trojan that could install a backdoor on the computer to allow criminals to access your computer. Even Avast has been mired in controversy by selling people's personal information at least two times. See the "Bundled Software" & "Malware Infection" section near the bottom of the CCleaner Wikipedia page:

https://en.wikipedia.org/wiki/CCleaner

Here is an article regarding Avast selling people's information:

https://arstechnica.com/tech-policy/2020/01/avast-kills-off-jumpshot-the-subsidiary-that-sold-all-your-web-data/

If you still have issues after uninstalling these types of apps, then run the third party app EtreCheck and post the report here so we can examine it for clues. FYI, EtreCheck does not require installation and can be run directly from the Downloads folder, so it won't affect system performance.