Across:
  1,4. Confusing expression of 26ac perhaps (6 8)
  10. It stands by the park, and often features in poetry (5)
  11.  Is more smashing than eruptions? (9)
  12,22dn. People connect by performing onanism and embracing snail abuse (2 3 2 2 6)
  13. If initially player lacks every ace, then fold  (5)
  14. Entering with headless horse (4)
  15. Public address: Religious Studies Ignore Eastern Illness (9)
  20. Experiment lit up, made 27ac of a wave (9)
  21. Teach about a lost grave (4)
  24. Hence both sides embrace a type of panel (5)
  26,29,30. Old 19 dn. at odds with an eye for an eye (3 6 4 4 1 5)
  27. Give credit for it - a butter churn (9)
  28. Serious fliers bring tail to the front (5)
  29,30. see 26ac.
Down:
   1. With such confusion, deem it an illness (8)
   2. Threat to mutilate emu with torture and middle of feet cut out (9)
   3. Faux NY rallies, a setting for return of vocal element of the people  (6)
   5. Vocal John wildly violent, knocking six out (5)
   6. Burly Pat bashed all at once (8)
   7. Ego, a strange game of projection (5)
   8. Imitation of otters at zoo (6)
   9. Reliable early region of historic Istanbul (8)
  16. Bad dog! Henry is number one at the table! (8)
  17. Mad bugger embraced 'X', and he pressed his way into history (9)
  18. Doing good by fellow man - this has to be right! (8)
  19. 26dn. head for food  (8)
  22. see 12ac.
  23. Rubber age deserts heart (6)
  25. Much of America described by dead language (5)
  26. Topsy's nose might run ... kindly restrict! (5)