Across:
   8,15dn,9. Torment in arrangment of animal's food - it's so hard to find (6 2 1 8)
  10. Acclaim for Australian briefly in New York  (8)
  11. Industrial fasteners removed first - they've been around longer (6)
  12. Feathered leader contradicts about flock's common ground (7)
  13. Shrink from a goblet (7)
  16. Hector Herbert and Leonard perhaps - they offer almost no resistance (15)
  19. Drug vendor offered revolutionary spray (7)
  21. Shrink from a cross (7)
  24,15dn,26. Warner one hopes 3dn. alive (6 2 1 8)
  27. Alpinist suffering chaotic descent (8)
  28. Leash your pet, even out of the city (6)
Down:
   1. Where the flock gather, at the side of the head (6)
   2. Lead arranged by helper in city (8)
   3. Paints perhaps fanciful US: free cars! (10)
   4. Flock see Harry Potter initially as corrupted (5)
   5. Rely on rebuilding an old instrument (4)
   6. A very hot one, he has a lion's heart in an artist's surrounds (6)
   7. A very hot one, she gets the point outside of company church (8)
  14. Digital protection for small pictures (10)
  15. see 8ac. and 24ac.
  17. Disruption of operative - he encounters rising lava (8)
  18. Prevails to push trim design (8)
  20. 23 ill (6)
  22. Rank fellow with a line (6)
  23. Not much of this can tally (5)
  25. Make sterile comeback for annoying noises (4)