9 across: Express disapproval of sweet-sounding retro artefact? (9)
This one’s amusing and it might have been put into DA Gold if the crossword overall wasn’t so tough. Here, though, we’ve got express disapproval = boo, sweet = meringue and sweet sounding = merang giving express disapproval of sweet-sounding = boomerang = retro artefact, and that last step, boomerang = retro artefact, is both funny and nutty.
7 down: High-class kiss blown in hearing? (3, 6)
I got this out because of cross clues, but that does not mean this one ain’t nasty. Here, kiss blown = skis, in = cool and in hearing = chool, giving kiss blown in hearing? = ski school = high-class (as in the class is at a high altitude).
Update: Although the following clue was originally considered nasty, TH put me on the right track in the comments and it’s now here for historical purposes only:
24 across: Scotch distiller pared technique linked to moisture (5)
I’m not completely sure how this one works, but it’s super nasty. Wikipedia tells me that Dewar was a Scottish chemist, or, as DA would have it, a Scotch distiller. How anyone else was meant to know that is beyond me, though. Moisture = dew, but I can’t explain the ar.