No 13664. Monday 19 Sep 2022, Dr. X

Solution to 7D has been deliberately left unsolved and is to be answered only by a non-regular / novice commenter, with proper annotation. Those who have answered earlier in the week, please give others a chance.

ACROSS

1   Comfortable clothes, popular for picnic (8) SINECURE {S{IN}ECURE}

5   Upset by couple of fellows breaking regulation (6) RUFFLE {RU{FF}LE}

10 Native American hut in hamlet, one in a higher position (7) WICKIUP {WICK}{1}{UP}

11 Centre hosting full moon party, close to Phuket presumably (2,5) NO DOUBT {N{O}{DO}UB}{p...eT}

12 Blow up as fool gets noisy (2,3) GO OFF {GOOF}{F}

13 Endless ruckus by deranged radical (9) ELEMENTAL {mELEe}{MENTAL}

14 What chauffeur might do to deceive? (4,3,1,4) TAKE FOR A RIDE [DD]

18 Particle physics concept is incorrect, trying other ideas finally (6,6) STRING THEORY {TRYING+OTHER+i..aS}*

21 Rising in an excited state, arousing date in bed (4,5) COUP DETAT  {CO{UP}{DATE*}T}

23 Priest avoiding extremes of avarice perhaps (5) VICAR {aVARICe}*

24 In my opinion, embodies ancient painting technique (7) IMPASTO {IM{PAST}O}

25 Greek character purloins mobile, runs away (7) UPSILON PUrLOINS*

26 Striking Oslo workers conducting a form of industrial action (2-4) GO-SLOW [T]

27 Give up or reduce consuming dope on reflection (8) ABNEGATE {AB{GEN<=}ATE} 

DOWN

1   Waste most of fixed allowance (6) SEWAGE {SEt}{WAGE}

2   Mexican dish in container returned by emcee unfinished (6) NACHOS {CAN<=}{HOSt}

3   Master thief turned into murderer (9) CHIEFTAIN {C{THIEF*}AIN}

4   Envy after record-breaking part in picture (14) REPRESENTATION {R{EP}{RESENT}ATION}

6   Dancing nude around university is excessive (5) UNDUE {UND{U}E*}

7   Female losing equilibrium finally fell in well (8) F?U?T?I? (Addendum - FOUNTAIN {F}{mOUNTAIN} - See comments)

8   Acclaimed former editor takes charge (8) EXTOLLED {EX}{TOLL}ED}

9   Completely dominated, he's turned on perhaps by spanking bum (5,4,5) UNDER ONES THUMB {HES+TURNED+ON}*{BUM*}

15 Social climber in French Riviera, excited to entertain starlet on vacation (9) ARRIVISTE {RIVIERA}* over {St...eT}

16 Preparing hot, spicy stew — extremely nourishing (8) PSYCHING {HOT+SPICY}*{No...nG}

17 Wins, waves shirt without hesitation — a bit of payback (8) TRIUMPHS TRIUMPHS {SHIRT}* over {UM}{Pa...k}

19 Brief inspection to tackle problem in plant (6) SCILLA {SC{ILL}An}

20 Breaking record — sportsperson's ultimate dream (6) TRANCE {TRA{s...oN}CE}

22 Detective consequently seizes cocaine in nightclub (5) DISCO {DI}{S{C}O} 

Reference List

Popular = IN, Fellow = F, Hamlet = WICK, Centre = NUB, Party = DO, Noisy = F, In my opinion = IMO, Runs = R, Dope = GEN, Record = EP(Extended play), University = U, Female = F, Editor = ED, Hesitation = UM, Detective = DI, Cocaine = C