is there a way to use CC4 to create a clothing morph such as a stretch / tear or a strap falling down that can then be used as a real time animated morph in iclone?

You have to use Morphs Creator for that.
In short:
Have the same clothed character in Morphs Creator and CC
In CC make necessary cloth modification and export as iAvatar.
Import that into Morphs Creator as a Morph (optionally bake multiple morphs into one for body/cloth morphs combo).
Send morphs update to iClone.

Is there a tutorial somewhere for this?

Is there a tutorial somewhere for this?         

Maybe there is some extensive tut, try search on tubes.

This is very quick one to get you started (or struggle :)).
For something more complex you probably want to morphs outside of CC and re-import.

Note: for tearing like this one, the mesh already have to be split.

Thanks for this.

There are cloth assets that are able to be morphed in real time inside iclone. 
"Shirt of her man" being one of them. All of the morphs are able to be animated in real time inside iclone.

My Morph Creator seems to be broken. It crashes whenever I attempt to create a morph.