I’m so glad it’s not just me struggling with this one. Other than 1, 18, 20 and 21 im utterly stumped. Just can’t get into the swing. Maybe come back to it tomorrow morning with a very large pot of coffee.
Castafiore,
In 11a “games” are letters 3 and 8. Then you have a repeating 2 letter word which slots in and out (if that makes sense).
The second word in 13a is literally a supplement to a (legal) contract. The two word answer is noted in Chambers as “Aust”.