4  Without this idea, human happiness ends (4)

 7  Same fine quality extract (5)

10 Egg's odour spills: this egg's good (4)

11 Simple objective: kick the POS out! (4)

12 Revolutionary selection from bard, eh? "Art" etc.?? Figures! (10)

13 Go through the Reverend's article (4)

14 River and mountain system of country (5)

15 Mythical king of Britain, one lacking in grey matter (4)

20 Threaten with brownie point cut, IRL! (7)

21 Follow in the footsteps of Alphabet alum, enjoy retirement stocks (7)

23 "It is incontrovertible, unfortunately," I vented (7)

25 Live together without a bit of conscience, embracing the ultimate libertine revolution (5-2)

26 Array elements 2 through 5 provide fast response (4)

27 Clean girl's chamber (5)

29 Accepted losing one medal (4)

33 Heartbroken thus, I, as mime-sans-compare, hide rage (10)

34 Happen to be a subject (4)

35 Noteworthy events, weather, sports primarily (4)

36 Fortunate old woman gobbles up the last snack (5)

37 Win the Ashes resoundingly (4)

38 Was able to understand ghost, oddly (3)

 1  Only the beginning and the end of travelogue is consistent with reality (4)

 2  Monster! So revolting! (4)

 3  Go quietly, sneak a look (4)

 5  Choppy ax use by gangster, someone not interested in doing it (7)

 6  Top waves, excellent! (7)

 7  Reminder: Honourable leader is in the clutches of corrupt CEO (4)

 8  He deals with applications and other arrangements for late admissions (10)

 9  Master list includes setter at the end (5)

10 A deliverer rushes (3)

16 Stand up to wash the bottom portion off (4)

17 Commit positive changes, avoiding move? Positive! (10)

18 Quick cheese fondue fountain! (5)

19 Essentially glum and bad side of the moon (5)

22 Make out with corrupt, top politician? Yes! (4)

24 Polishing off one last piece of meat fried in butter as a power source (7)

25 Pay for kinky pornos after a bit of self-indulgence (7)

26 Dull sequel lacks heart (5)

28 Boy's heart usurped by you and me getting engaged (4)

29 Band's opening number breaking silence (4)

30 About to fill glasses? Sweet! (4)

31 Amphibian's unused bottom part? (4)

32 Rising sea levels ultimately point to carbon dioxide, perhaps (3)