Thanks. I think my problem with this puzzle is that, at least traditionally with cryptics, there should be a definitional element in the clue. So, for example, the clue might have read "Dr. Castier gives up."
That's why all those without strict definitions had question marks - that tells you something untoward is going on. Paul used to do ones like today's quote often. I think it actually helped having several of them. I don't think it is outside of crossword clue grammar but it is quite challenging when first encountered. I thought today's puzzle very refreshing.
"Ground" as in minced. All sorts of similar words can mean look for an anagram.
Now you should have the last letter of 12ac; think of sound, as is, say, telephone, gramophone, etc, etc.
Not just difficult, but unfair - and ugly. I can just about live with the lack of definition in the themed clues, but Paul is surely out of order with, for example, 'Went I re hole?' A cryptic clue must be a comprehensible English sentence or phrase, not just a random set of words. And 'Dr Castier' is just lazy setting. Anyone can invent a surname.