My First Cryptic, by AC

1234567891011121314151617181920
Across
  1. 7. Origin smashed a sorbet night (8,4)
  2. 9. Sport car (4)
  3. 10. Monika recorded tin level (7) (#3)
  4. 11. Corgi plays with flounder, not president or half-Estonian as favourite pastime (9)
  5. 13. #3's shared feeling almost sounds like slumped five (4)
  6. 17. Testament to your unending bond with setter? (4,3,5,2) (#6)
  7. 18. Nitric oxide provides alternative to #16 if you need it (2)
  8. 19. Replying to #6 requires a year's fringes (3) (#16)
  9. 20. Our next purchase together will hopefully be found in aspirin grocer (4)
Down
  1. 1. Curved before Julia's boyfriend became local hangout (9)
  2. 2. Clue: your favourite (8)
  3. 3. Leaders of intriguing knight's establishment are actually furniture moguls (4)
  4. 4. Spooner finds period piece in bar game reverberation (7)
  5. 5. Drug-free heavy biscuit is first Christmas present (6)
  6. 6. First rendezvous was at defiled drug hill sandlot (5'1,9)
  7. 8. Joiner loses supermodel for #3's first home (3)
  8. 12. Team exclaims over distance! (7)
  9. 14. Semi-spiced semi-Asian soup not a good idea for baby (6)
  10. 15. Nolan heard weekend getaway for #3 (6)
  11. 16. Modern English town is favourite destination (3,4)