No 13800, Tuesday 28 Feb 2023, Bruno

Solution to 16A 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   Old and reticent person on a tram in Oklahoma's excited! (11,4) EXCLAMATION MARK {EX}{CLAM}{A+TRAM+IN+OK}*

9   Person who receives an older relative with small peg (7) GRANTEE {GRAN}{TEE}

10 Parent partial to love goddess - short like Napolean? (7) PARVENU {PARent}{VENUs}

11 Ray of moonlight's starting to appear after galestorm (5) GLEAM {Mo...t}<=>{GALE}*

12 Spooner's secure with fake weapon (9) MATCHLOCK (~latch mock to mocklatch) 

13 Should hiding love and pain be a sign of masculinity? (9) MOUSTACHE {M{0}UST}{ACHE}

15 Company spends regularly to advance grass (5) SEDGE {GE}<=>{SpEnDs}

16 Fabric's ninetyfold firm at one end tied in knots, when separated, collapses (5) N?L?N (Addendum - NYLON NiNetYfOLd* - See comments) 

18 Namedropping in private to get alliance, essentially, among other things (5,4) INTER ALIA {INTERnAL}{allIAnce}

20 Concerned with city losing inhabitants? Stick with this method of being green (9) RECYCLING {RE}{CitY}{CLING}

23 Hairy Emma intends to get shaved regularly (5) MANED {eMmA+iNtEnDs}

24 Until any individual starts mutating, these animals can only be found in water (7) NAUTILI {UNTIL+Any+In...l}*

25 Art form at its core's one form of magic, mostly (7) ORIGAMI {fORm}{1}{MAGIc*

26 Poor? Adapt fresh crops for cultivation (8,3,4) STRAPPED FOR CASH*

DOWN

1   Digital bands playing in German get invited to England's south (10,5) ENGAGEMENT RINGS {IN+GERMAN+GET}* in {ENG}{S}

2   Drinks at posh house (7) CHATEAU {CHA}{TEA}{U}

3   Robot from America plants vegetable in empty urn (9) AUTOMATON {A}{Ur{TOMATO}N}

4   Sailor's crew dumps leader to one side (5) ABEAM {AB}{tEAM}

5   Indian politician - one kept in a temporary location is tense (9) IMPATIENT {I}{MP}{A}{T{1}ENT}

6   No further disrobing, One Direction! (5) NORTH {NO}{fuRTHer}

7   Tissue obtained from dead criminal contained no Iodine (7) ADENOID {DEAD}* over {NO}{I}

8   A punch on the mouth and chin wacked, slunk away (7,8) KNUCKLE SANDWICH*

14 Half of critters on ice eat fish's heart - that's savage (9) CRITICISE {CRITters}{IC{fISh}E}

15 More thrifty small credit supported by setter's platform (9) SCRIMPIER {S}{CR}{I'M}{PIER}

17 American city on the outskirts of Chandler needs to obtain what in Mexico would be "polish" (7) LACQUER {LA} on {Ch...eR} over {QUE}

19 Plant - an acacia surrounding another plant (7) LANTANA [T]

21 Communist Party recruits that man - an animal (5) CHIMP {C{HIM}P}

22 Sticky substance's very loud to detonate (2,3) GO OFF {GOO}{FF}

Reference List

Old = EX, Oklahoma = OK, Small peg = TEE, Company = GE, Name = N, Concerned with = RE, England = ENG, South = S, Posh = U, America = A, Sailor = AB, Indian = I, Small = S, Credit = CR, What in Mexican = QUE, Communist Party = CP, Very loud = FF