Thank you all three. Time will tell if the suggestions have worked as the issue while really annoying with a 94Gb memory hog it is only intermittent. But 94Gb is a lot if you 'only' have 24Gb as I remember when 256kb extra was a lot [of RAM and £/$/€]!
In order of emails, at /Library/LaunchDaemons I found com.macpaw.CleanMyMac-setapp.Agent [I thought I'd got rid of CleanMyMac] long ago and com.malwarebytes.HelperTool [ditto].
In Terminal 'pkgutil --pkgs | grep -i cleanappdaemon' did not produce what I think you hoped for:
Last login: Fri Oct 23 10:03:47 on ttys000
Colins-iMac:~ CC$ 'pkgutil --pkgs | grep -i cleanappdaemon'
-bash: pkgutil --pkgs | grep -i cleanappdaemon: command not found
Colins-iMac:~ CC$
Finally, I did not need Findanyfile as I realise I had EasyFind and it found com.syniumsoftware.CleanAppDaemon.plist containing Library/Application Support/CleanApp/CleanAppDaemon.app in ~/Library/Preferences/. I don't think the contents of a plist can do any harm, unless there is something to read it. Anyway, I've trashed the plist and assume anything that needs it will recreate it. plist attached.
I run Sophos, but did not know they had a first rule!
Thanks, Colin