No 13276, Thursday 17 Jun 2021, Afterdark

Solution to 21D 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   Give up, at one vacate bed that is being occupied by Tom (8) ABDICATE {A}{BeD}{I{CAT}E}

5   Fruit, cherry in the core is more foul (6) UGLIER {UGLI}{chERry}

10 Perhaps an Iranian, is nowhere near by metric system (5) FARSI {FAR}{SI}

11 Married? Yes and sad by middle of the week, perhaps (9) WEDNESDAY {WED}{YES+AND}*

12 Note in second book, we had on description of exoskeleton (9) CHITINOUS {CHIT}{IN}{bOok}{US} Thanks to Google

13 Held by inappropriate ethics; they are in the mouth (5) TEETH [T]

14 Shocked a girl, her arm struck, throbbing basically (6) AGHAST Acrostic

15 Dynasty of father’s lavish indiscriminately, losing dollars (7) PAHLAVI {PA}{LAVIsH*}

18 King perhaps providing franc to university (7) CARDIFF {CARD}{IF}{F}

20 Sharp as tack primarily, you reportedly emptied treasure (6) ASTUTE {AS}{Tack}{(~you)U}{Tr...rE}

22 Wolfram, core of it is used by plant life (5) FLORA {wOLFRAm}*

24 A bridge perhaps at Cuba closed as Ross passed (9) CROSSOVER {C}{ROSS}{OVER}

25 Got alibi? Because at first they can't be omitted (9) OBBLIGATI {GOT+ALIBI+Be...e}* Anind missing

26 Sometimes used while cooking; pan, RO? Perhaps (5) APRON*

27 A catch held at the end, Victor dropped in match getting tense (6) DETENT {helD}{E(-v+t)TENT}

28 Loses due to nervousness, hope sucks almost; terrible (6,2) CHOKES UP {HOPE+SUCKs}*

DOWN

1   Change result by replacing novice finally with adult (6) AFFECT (-e+a)AFFECT

2   A pistol Ruby returned clipped off finger tip when held by radical (9) DERRINGER {RED<=}{(-f+r)RINGER}

3   Outrageous isolation, no law left or act to make it illegal (15) CRIMINALISATION {CRIMINAL}{ISolATION} 

4   A small vessel to wrench primarily, big round and tapered at the top (7) TOWBOAT {TO}{Wr...h}{B}{O}{And}{Ta...d}

6   Remarkable race, perhaps, dashes in the middle; boat and fish (5,5,5) GREAT WHITE SHARK {GREAT}{WHITE}{daSHes}{ARK}

7   A small studio perhaps gets popular director on to 4th & 5th movie (5) INDIE {IN}{D}{movIE}

8   Regular myth, rich are spoilt (8) RHYTHMIC*

9   Makes sense for a date to cook spud (4,2) ADDS UP {A}{D}{SPUD*}

16 Perhaps Norton is against six; primarily routing everyone (9) ANTIVIRUS {ANTI}{VI}{Ro...g}{US}

17 A very loud lecture outside on platform (8) SCAFFOLD {SC{A}{FF}OLD}

19 A beauty treatment for female? A govt agency launches first (6) FACIAL {F}{A}{CIA}{La...s}

20 Doctor has boil to get rid of (7) ABOLISH*

21 An agreement perhaps is pure counter — play on words, if not unsatisfactory (6) ?R?N?P (Addendum - PRENUP - {PuRE}{PUN<=} - See comments)

23 Cycle is at gate for a short while (5) ORBIT {OR}{BIT}

Reference List

Dollars = S, Franc = F, Victor = V, Tense = T, Adult = A, Radical = R, No = 0, Law = L, Big = B, Popular = IN, Director = D, Date = D, Very loud = FF, Female = F, Unsatisfactory = U, Gate = OR