Across:
   1. Too much drug-taking in prison environment for 30 town with 29 of 20/5 13 ('16, '17, '18)...  (6)
   4. 18 stir west nastily (8)
  10. No time to relent - pain gets worse year after year (9)
  11. Who lugs around pointless eater of corpse? (5)
  12. They take drugs in surer form (5)
  13. Rent does include a 4 (9)
  14. Valence jumping gives isolated location (7)
  16. I'm more hazy in recollection (6)
  19. Group rang El Salvador hosts (6)
  21. Slammed door before your 23 departure from 30 (7)
  23. Greeting both sides in Word War I, New Delhi causes big stir (9)
  25. Precious piece of livestock held in jail's walls (5)
  27. Wrong action of the foot? (5)
  28. City player got bowler perhaps to hide (9)
  29. Producing a rabbit or three? (3-5)
  30. State removed core of farm from territory (6)
Down:
   1. Took hold of and cared about shot put (8)
   2. Off-grid energy sounds dismal (5)
   3. Places and stuff? (9)
   5. Heavy metal beasts (7)
   6. Letter from Europe spells out aims around Greek capital (5)
   7. This profession is cool - get involved! (9)
   8. Are out to spare whip, making big impression (6)
   9. I rue TV's poor quality (6)
  15. Able to hold water and land (9)
  17. Aura in jam made a contribution to the number (9)
  18. 13 superficially copy copies (8)
  20. Part of corpse is microbes changing the 3 (7)
  21. Did gun go off getting spruce? (6)
  22. Change for Glinda in Oz (6)
  24. Not yet consumed in the hands (5)
  26. Being teetotal was about power (5)