Across:
   1. Not even adults in same condition (6)
   5. 19 idea of article is bats**t crazy around rumouring 1's 8 origins (8)
   9. see 4 down
  10. Got heavy-footed with gas pedal essentially (4)
  11. Untruth about, say, authority (5)
  12. Not having company, envies people who work with animals (4)
  13. This could cut through warm safe arrangement (5 3)
  14. Illegal sex? Cue the defence! (6)
  15. Classic figure carved on dais? (6)
  18. Conspiracist loonies crave stumuli &anp; feedback too, so facebook ends up most insane (8)
  21. Liquidates, having no hesitation with offers (4)
  22. Greek Australian comedy character with brief fiery run (5)
  23. Part of unclean uses? (4)
  24. They try to combat cancer (and hair disaster!) with bits of pot (15)
  26. Moved ahead of lead van ceding passage (8)
  27. Can let off publication? They did retract 5 down's dishonest work! (6)
Down:
   2. Union terrific at containing rampant leader who takes over (7)
   3. Deviating in time, 10 around first of many barriers (11)
   4,9ac. As an umbrella mess, lumped awkwardly together, three things treated with one 12 down? (7 5 3 7)
   5. He did famously 16 with 27 article linking 1 (via 8) with the 4 9 12 down and, with article depicted, stir branch of academia (6 9)
   6. Find sweetheart in statuesque Ezekiel (7)
   7. Display of lottery excluded, and alcoholic beverage (3)
   8. No right to be involved with treatment of clitoris irritation (7)
  12. Shot scenes with only seconds to go in break (11)
  16. Fear dud treatment is rip off (7)
  17. One who questions, challenges, mobilises, pickets (7)
  19. Mostly arranged Ravel within original boundaries (7)
  20. Demolish cryptic clues about island race (7)
  25. Display of odds excluded, and alcoholic beverage (3)