Across:
   1,4. Young star's name on cross after Viper heroin disaster (5 7)
  11,24dn. Popular Indian playing parts in South Africa (if mostly similar) with unchanged heart (4 3 4)
  12. May incur a torment, only keeping some material? (7)
  13. Breaks are a must for hobbyists (8)
  14. Complained when I'd performed (6)
  16. Spot on Bishop's patch? (3)
  17. Podcast sitcom or blog? Or put in 'mutant ape' special? (11)
  18. Untamed hot brats, her idols! (11)
  20,10dn. Light-beam energy extracted from food and inter-space travel among the things he wrote about (3 8)
  21. Working of sun about it primarily (6)
  22. Choke lad when this goes wrong? (8)
  26. Signs up as student, joining throng of sad loners (7)
  27,16dn. Leaders of chess league are unsure, and differ about like check I model (7 8)
  28,29. She crossed swords with Flynn but briefly, not having the time to be "mature ten" to that rat! (7 1'4)
Down:
   2. Ape and I have sex, embracing it (7)
   3. Wipe out before quarter time (5)
   5. Cut poor performer (4)
   6. Gadgets that seem to be quiet... but put in, one hears well (9)
   7. Concentrated on playing tennis around middle of set (7)
   8. Much of the world backing "first thing's first" (4)
   9. Structure where rich are fixed within heavy walls (9)
  10. see 20 across
  15. Lack of strength seen in fellows taking marijuana and then getting into ice (9)
  16. see 28 across
  17. Tribe pool resources and work to keep the wolves from the door (9)
  19. Aluminium taken from country to country (7)
  20. Make new arrangement for wind instrument without cheesy lead (7)
  23. Hated calamity? (5)
  24. see 11 across
  25. Small portion of land is mostly rented (4)