Castiel falls into step behind Dean and Phil, leaving a gap between himself and them to give them space. He keeps close enough to hear their conversation, and to react swiftly enough should anything attack, but he knows Philip still cares little for him.

And Clarence perplexes him: Castiel's gut response is to dislike and distrust... him, it, whatever the proper word is. He is obviously indwelling Philip without his desire or permission, and that is far too demon-like for Cas' comfort, waking his desire to smite, to purge impurity. But as far as he's seen (so far), Philip also seems to mostly retain his autonomy. And since Cas can't tell yet what Clarence is, he has no clear idea how to exorcise him from Philip without killing both of them.

So he contents himself with quietly following behind, vigilant to sounds in the forest around them as they near the mansion. It is not lost on him that he is deliberately putting space between himself and Dean, too, keeping his yearning in check. Now isn't the time... yet.