Solution to 14A 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.
Open for anyone to answer, if not solved by 1 PM.
ACROSS
1 President's mail disseminated, one caught in lie on expansion (13) AMPLIFICATION {P+MAIL}*{FIC{A}TION}
10 More calls made to everyone in the contest (3-6) ALL-COMERS*
11 Location's smell almost getting stale at the end (5) SCENE {SCENt}{s..lE}
12 Middle Eastern custom is unoriginal (5) TRITE {easTern}{RITE}
14 To fawn over Labour's ridiculous basically (6) S?A?E?
16 First Lady arrives at new flat (4) EVEN {EVE}{N}
19 Approach firm backed by setter (4) COME {CO}{ME}
20 Analyst working after removing variable sideways (6) ASLANT ANALyST*
25 Zero time to pacify outside. It's Hate (9) ABOMINATE {AB{0}{MIN}ATE}
26 Small success in hiring a country lad (5) SWAIN {S}{W{A}IN}
27 Point at tenor instrument (5) THORN {T}{HORN}
28 Reject most, starting late, ones in contest (9) OSTRACISE {mOST}{RAC{1'S}E}
29 Associates almost grab bishop and speakers (13) COLLABORATORS {COLLAr}{B}{ORATORS}
DOWN
3 Free bathrooms at England (5) LOOSE {LOOS}{E}
4 One that provides food takes charge at Delaware against resistance (6) FEEDER {FEE}{DE}{R}
5 User gets copper's book to read (8) CUSTOMER {CU'S}{TOME}{R}
6 Sat in the counter in front of television, scenes lack substance, insipid (9) TASTELESS {SAT<=}{TELE}{Sc..eS}
7 At almost one, two directions anyway empty, it's unidirectional (3-3) ONE-WAY {ONe}{E}{W}{An..aY}
15 Loving action after break essentially, a little (9) EMOTIONAL {MOTION}<=>{brEak} and {A}{L} L for Little?
18 Arrogant knight (8) CAVALIER [DD]
21 Subway has a huge cask to hold 50% of fennel (6) TUNNEL {TUN}{fenNEL}
22 Scan topics covering part of a poem (5) CANTO [T]
23 Architectural style from cutting rock at one end, retain the middle and keep an opening (6) ROCOCO {ROCk}{rOCk}{O}
24 Division of Securities & Exchange Commission to counter disintegration (6) SECTOR {SEC}{ROT<=}
26 Introduce small pastry (5) START {S}{TART}
Reference List
President = P, New = N, Variable = Y, Small = S, Tenor = T, Bishop = B, Golf = G, England = E, Resistance = R, Read = R, Navy = N