I have a little over half the grid filled but have jaloused the statement, theme and rationale. What a very clever piece of construction! Thank you, Karla - now to complete the puzzle.
I'm deeply puzzled by 6d Princely family once crashed Volvo with tail end gone (4), and could do with a prod (definition?) on 26a Civil service department cut off (6)
Thanks Longhare. (Are you a new poster, I don't recognise your name?) I now have a full grid with 17 clashes and still no clue what's going on.
I guess I have to try to find an anagram of seventeen mainly very common letters!
I had finished the grid with only 16 clashes. A misreading of chambers led me to believe that one altered word was actually the answer to the clue instead. Fortunately the nature of the theme and the clashes made it very doable to hone in on the missing piece.