James is getting a bit frustrated shut up here, he tries not to show it but I can tell - also, Dumbledore's still got his Invisibility Cloak, so no chance of little excursions.
Harry Potter and the Deathly Hallows
I feel "shut up" is a noun phrase in this context, meaning confined. But I couldn't find it a noun phrase in any dictionary. So, I'm not sure if my understand is correct. How should we understand it?