Having taken a knock? (3)

I believe the answer is:

out

I'm a little stuck... Click here to teach me more about this clue!

But I can't explain it at all! Could you help me understand?

(Other definitions for out that I've seen before include "Not favoured" , "A way to escape" , "Mistaken; unconscious" , "On strike - dismissed - unconsciousout" , "Known" .)

I've seen this clue in the Evening Standard.

Want a hint initially instead of a full solution? Install my app