Solution to 16D 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 Dilapidated mine hidden by "Private" sign (6) GEMINI {G{MINE*}I}
10 Freezes pickles to finish off, per Spooner (5,5) KEEPS STILL (~steeps kill to keeps still)
11 Those people's leader killed for the next in line (4) HEIR tHEIR
14 Once, Singh has frequently filed stable reports? (6) NEIGHS {oNcE+sInGh+HaS}
15 Please switch off? (7) DELIGHT {DE-LIGHT}
17 Selection of top end antique hanging (7) PENDANT [T]
20 Sadly rejected morning greeting (6) SALAAM {ALAS<=}{AM}
22 Epic of an army fighting to save Sita, ultimately close to Lanka (8) RAMAYANA {AN+ARMY}* over {sitA} and {l..kA}
24 Polish chiefly brightening up faded furniture (4) BUFF Acrostic
25 Huge island warring became neglected (10) LANGUISHED*
27 Expect gangster to conceal hint in treason (8) BETRAYAL {BET}{AL} over {RAY}
28 Threads covering oriental pines (6) YEARNS {Y{E}ARNS}
DOWN
1 Make fresh green tea (8) GENERATE*
2 Stubbing member's foot softly, walk unsteadily (4) LIMP {LIMb}{P}
3 Party food includes extra spicy, tasty appetisers for starters (6) FIESTA Acrostic Semi&lit
13 Book in Hindi initially isn't available to translate a Rahman film (6,4) ANIMAL FARM {A+RAhMAN+FILM}*
16 Mountain ash layer scattering this range with neutrons (8) H?M?L?Y?
18 Parts of snake repeatedly used in Chinese clothes (8) NANKEENS* [Letterbank]
19 Twist removing a clear plastic around tattoo (7) CRINKLE {CLEaR}* over {INK}
21 Hysteria cum envy constraining judgement (6) ACUMEN [T]
26 Battle arising from strikes (4) SPAR<=
Reference List
Private = GI, Active = A, President = P, America = A, Gangster = AL(Capone), Oriental = E, Softly = P, Old = O, Posh = U, Lecturer = L, Positive = P, Male = M, Ancient city = UR, Illusion = MAYA