Thanks for confirming 28d drxx - the PDM has just occurred - what a brute of a clue! I now (eventually) have a full grid, just need to sort out 6a,6d,10a and 29a. Still baffled by how the six forming a cycle work.
Gitto, the so-called cycle of 6 took me longer than the whole of the rest of the puzzle. I found the word 'cycle' didn't help. Perhaps I've got it wrong but the answers I've got seem to work.
it mentions that the "cycle" of six are thematic - but i dont really see it. is there a reference im not aware of (think the theme was a little ahead of my time)