1.  2.  3.  4.  5.  6.  7.   g
  g   g   g   g   g   g   g 8.
9.          g 10.     
  g   g   g   g g g   g   g  
11.        g 12.       
  g   g   g g g   g   g   g  
13.      g 14.         
g g g g   g   g   g   g g g g
15.  16.        g 17.  18.  19.
  g   g   g   g g g   g   g  
20.        g 21.       
  g   g   g g g   g   g   g  
22.      g 23.         
  g   g   g   g   g   g   g  
g 24.              

Warning

24-Across and 6-Down are not "proper" phrases - ie not established idioms.

On the other hand, the mystery expressions starting at 1-Across and 1-Down are perfectly legitimate, and indeed complementary.

ACROSS

1,21. ? (6,6,2,7)

9. Bouts of chaos - less lines. (9)

10. Some boys pit empathy against enmity. (5)

11. Regular strange light in New York. (7)

12. Defence has a big thing about war. (7)

13. Knock back oil of leaf. (5)

14. see 3-Down

15. see 1-Down

17. Waiter returns fine webs. (5)

20. Number of Bond's little curtain. (7)

21. see 1-Across

22. Away from home in Rome: and embracing the odd local peace. (5)

23. see 1-Down

24. Concocted a rent mixup - a friend's job! (2,3,9)

DOWN

1,15,15-Across,23-Across. ? (5,2,6,9,9)

2. Pirate sick, bringing up large bits out of gut. (7)

3,14-Across. Waves "no" to me, tracing delicate air-letters. (15,9)

4. Outwardly, siblings were bossy with sook. (5)

5. No bet for such beasts. (3)

6. I bear a "yes" - allege as wildly as you will! (6,9)

7. One craft or one game, one dismisses the east. (7)

8. Figure performed once with Rook and King. (6)

12. Pass time with some plumbing. (5)

14. Rear of modern era is end of time. (5)

15. see 1-Down

16. Plays company, plays music. (7)

18. Arranged abridged instruction. (7)

19. Made ass of - stuffed up (cumulative). (7)

21. Poplar sword is not as mighty ... (5)

23. ... as legendary bird's back, or capped head. (3)