How to do a OS 10.14.5 clean installation

RandyK56 wrote:

How do I do a clean install of MacOS 10.14.?

Apple does not use that terminology. To erase your Mac read Erase a volume using Disk Utility on Mac - Apple Support. You will be following the first bulleted item in Step 2.

To subsequently install macOS, read How to reinstall macOS from macOS Recovery - Apple Support.

... but perhaps you should explain exactly what you want to do, and why.

Why do you think you need to do a so called "clean" install?