Hi Helix,
Welcome to the forum.
What version of Opus are you using?
I'm not sure what you mean by 'clear' button? (one would interpret this as making the contents of the input box variable blank/empty)
In your password input box, (or your last input box) that you wish the focus I-beam to disappear, go to the input box's Properties Tab >> Text Input Tab >> and untick the option "Return skips to next text box". That should make the focus I-beam disappear.
If this is not suitable, then as "bwpatric" suggests, you can use some OpusScript to set focus to another object on your clear button. (sometimes a tiny delay works best when changing the focus, using the SetFocus() script.
As usual, Duncan is too quick and beat me to answering the tab order question.