Solution to 18D has been deliberately left unsolved and is to be answered by a non-regular/novice commenter, with proper annotation. Those who have answered earlier in the week, please give others a chance.
Open for anyone to answer, if not solved by 1 PM.
ACROSS
8 Daughter & son expelled from Budapest oddly cheerful (6) UPBEAT BUdAPEsT*
9 Spooner's female animal sickens, sends away to destination by plane (8) AIRMAILS (~mare ails to airmails)
10 Access transport (8) ENTRANCE [DD]
12 Reprimand student leader of institute at first and release (8) LIBERATE {BERATE}<=>{L}{In...e}
13 A lawyer limits information to items on the list (6) AGENDA {A}{GEN}{DA}
14 This worry duly affected young ladies (7) AGONISE {AGONISE+DULY}* = YOUNG LADIES [CA]
17 Study this site regularly for one working with canines (7) DENTIST {DEN}{ThIs+SiTe}
20 Spice container overturned by little woman (6) NUTMEG {TUN<=}{MEG}
25 Appallingly, a scar seen around one part of the lung (3,3) AIR SAC {A+SCAR}* over {1}
26 Firm about basically selling off musical instrument (8) RESOLUTE {RE}{Se...g}{Off}{LUTE}
27 Major celebrity playing games with sailor (8) MEGASTAR {GAMES*}{TAR}
28 Summon judge after rabbi's knocked out by a follower (6) BECKON (-r+b)BECKON
DOWN
1 Son awaiting disbursement of money (8) SPENDING {S}{PENDING}
2 Primarily, director establishes clear rules, ensuring equity and order (6) DECREE Acrostic
3 Mostly tolerate unknown amateur's lines (6) STANZA {STANd]{Z}{A}
4 Food supplier made a mess of terrace (7) CATERER*
5 Serbian boy beaten up somewhere in Australia (8) BRISBANE {SERBIAN+B}*
6 Try drinking Italian wine, it's most flavoursome (8) TASTIEST {T{ASTI}EST}
7 Red-faced female aristocrat seen outside inn initially (6) FLORID {F}{LOR{Inn}D}
15 Soldier from the south to demand a royal salutation (8) NAMASKAR {MAN<=}{ASK}{A}{R}
18 Reportedly failed to elude authority (8) S?N?T?O? (Addendum - SANCTION (~sank shun) - See comments)
19 No time? First try cooking Chinese style dish (4-3) STIR-FRY {FIRST+tRY}*
21 After being written up,some cadet in Utah co-operated (6) UNITED [T<=]
23 On reflection, one graduate identified Japanese condiment (6) WASABI {1}{BA}{SAW}<=
Reference List
Daughter = D, Son = S, Student = L, Lawyer = DA, Information = GEN, Old queen = ER, About = RE, Sailor = TAR, Rabbi = R, A follower = B, Unknown = Z, Amateur = A, Boy = B, Female = F, Royal = R, Time = T
