Clara suggested that the Doctor should do the Addams Family thing in order to get out of the way of the oncoming subway train. And by "thing", she meant Thing - the disembodied "Hand of Glory" that served the Addams Family.
Toobworld Central is always going to ignore actual references to TV shows that should be sharing the same dimension. But we're in luck in this case because of the two theatrical movies which starred Raul Julia and Angelica Huston. In the context of the Earth Prime-Time "reality", those movies were based on a real family. However, Clara might not have known that.
The Doctor, on the other - ahem - hand (Sorry about that, Chief!), might not have ever seen the films. And yet he understood the reference and finger-walked the TARDIS like a hermit crab out of the way... if only momentarily.
I'd like to think that the Doctor (in some previous incarnation) might have met the real Addams family, perhaps even took at least one of them along in the TARDIS. (Considering his other choices for companions, the money is on Wednesday. But I think Fester would be more fun!) If so, the Doctor would have known the real Thing.
And so a Zonk would be diverted.