Complete
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7 9 16 17 20 22 1 12 13 2 18 3 10 23 8 11 21 4 14 19 5 15 6
  1. 1a On the dot (6)
  2. 4a Room on board (5)
  3. 7a Political region in Switzerland (6)
  4. 8a Explode (4,2)
  5. 9a Active volcano in Sicily (4)
  6. 10a Toll road (8)
  7. 12a Tree on coast (anag) – shrub with bright red berries (11)
  8. 17a Unflappability (8)
  9. 19a Snide remarks (4)
  10. 20a Arboreal lizard (6)
  11. 21a Brought up (6)
  12. 22a Newspapers, TV, radio, etc. (5)
  13. 23a Proverbs (6)
  14. 1d Credit and debit cards (7)
  15. 2d Pariah (7)
  16. 3d Contrition (9)
  17. 4d Punctuation mark (5)
  18. 5d Type of knot (7)
  19. 6d Kid (6)
  20. 11d Relieved of anxiety (9)
  21. 13d Grandiloquent (7)
  22. 14d Dignity (anag) (7)
  23. 15d Return to a less developed state (7)
  24. 16d Division into opposing factions (6)
  25. 18d Old Japanese assassin (5)