I'm not sure about 10a, but I have a word that also means part of Yorkshire! When you take the theme word away you're left with Freud's Latin word for the "basic instinct". Does that make sense to you?
............and my solution to 21a is what C. was; I can only see the theme word (very short version) +abb. Church of Rome + synonym for visionary . Ah, I see it now, I think: first letter of Rome to go in! Good job you asked!
I'm finished and have gone through this thread, but as far as I can see, not all the answers are themed. 15ac and 26ac look like straight clues to me. Can anyone help with the parsing of 4ac?
I'm sorry, I don't follow your thing about Egyptian & king preceding: surely I haven't got the wrong answer? They certainly spit in a very unpleasant fashion!
For 15a you have to remove the theme word before making the anagram.
With 26a I'm still waiting for some explanation myself: my answer works perfectly without, as I said at the beginning!