I've seen the significance of the K - I think it's a bit weak.
I'm still stuck, though. Any hints on 2d ?
Rat-a-tat in advance (8)
I have ?P?S????
Also a hint on 6d would be appreciated
Hotel option when you've come to visit (4-2,4)
?A??-??-???? (I said I was stuck!)
Finally, does 21 start with C? I can't parse my answer.