Across:
   1. Philosophy which may see one 17 18ac ? (5 3 4 3)
   9. Frisky action is how to make the duvet warmer (9)
  10. Musician passed a knife (5)
  11. Father leaves a quarter, say, for moving about (6)
  12. Write song with 24 dn (8)
  15. Poles leave chaos for place in bondage (7)
  17,18. Liberal let chaste biker indulge in child's treat  (4 3 7)
  19. It sounds like they have wine and you can buy from them (7)
  21. Was wobbly socialist following the leaders of the east, even the enemy? (8)
  22. Does he ski mostly? (6)
  25. Pigment mixing: tedious task (5)
  27. Able geeks, even Pierre, regularly involved in fructose production (9)
  28. Was overcome with anxiety to prevent the daily disaster (15)
Down:
   1. Losing weight in initially wild animal phase (7)
   2. Inclination of point in strip (5)
   3. Philosophy which may see one 17 18ac ? (3 3 2 3)
   4. Bit of orchestra heard - oh lover! (4)
   5. Magic Rod has lost lustre, needing a change of scene (10)
   6. Fisherman able to provide catch (3)
   7. Young keep to urban setting (9)
   8. Framework of revolutionary letters (7)
  13. Lock cell! She strays - was found in contrary Mary's garden (11)
  14. "Get Back" together with "Bless Me" are given new arrangements (10)
  16. Sets apart funky vehicle (9)
  18. Engage Liz about nonsense (7)
  20. Purged lunatic, so cured (7)
  23. Two bits worth of food perhaps (5)
  24. Speculate about point's inclination (4)
  26. Make blueberry filling (3)