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)
16 Fabric's ninetyfold firm at one end tied in knots, when separated, collapses (5)
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}*
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}
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}
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