You can view the page at http://www.rugbyrefs.com/content.php?381-Understanding-Clear-Obvious
If you see a crafty punch to the kidneys, that no one else has noticed, it's clear. But it wasn't obvious
That's how I understand it.It's not mean to be broken down into individual bits. It's a term to mean unless I am 100% sure I am not blowing this whistle.