I confess I slumped when I saw it was Paul. I used to be on his wavelenght, but no more. I got 13ac, but like Brendan had never heard of it. I got 4 down but can't parse it.
I wondered why the capital letter to Duel, one of my favourite films, so thought of this director. From the thread I got 12 the name of my favourite Salvia. But I'm quite stuck. I'll work on a few more and no doubt be back for hints. I haven't quite worked out what the anagram is in 19ac, but I'm guessing the answer isn't small child.