Excuse my absence, Demeter - I'll be out again this afternoon too. Down answers are entered normally except for one letter which gets dropped to the end.
18 was a word I'd not encountered before, only got it because I'd been able to fill 4 of the checked cells.
If you've got the theme (through the moved letters from across clues), identified the production and secret sign, then solving becomes progressively easier. No twists in the tail. The 'Contest' is a subtitle of the production, supplied by the wiki site.
Strange to have such a heavyweight puzzle for a theme so flyweight.