As you may know, Android clipboard content and its changes can be got by any app, which is a security hole if you care about it(more info here). Any app can get your copied password, credit card numbers, and more.
Android has AutoFill or other mechanisms to handle sensitive info. Android Q also fixes this problem partly. But there are still some ways to bypass the limit, like using accessibility services and showing a transparent window.
ClipboardCleaner can't protect your passwords from being got by any app(after all, it's a security hole). But it gives you ways to check and clean your clipboard.