"Oh, that's not boring. That's very... not boring."
"You're going to save me. You're the Doctor. That's what you do."
So, Clara is hanging half in, half out of the TARDIS while it is flying over London. Where is OSH?
"She enjoyed that ... way too much."
"Name, species and reason for asylum?"
"Infinite lifespan, finite memory."
"Still saving the world from me?" "It's still here, isn't it?"
"When I look at you, I can't tell your past from your future, and there's so very much of both."
"The Doctor is no longer here! You are stuck with me!"
"I'd strongly advise you to keep out of my way. You'll find it's a very small universe when I'm angry with you."
... And so Clara's out of the series for, basically, being too bloody smart for her own good. Being too bloody smart for her own good isn't exactly out of character... but this was still rather a surprise.