No 12711, Thursday 22 Aug 2019, Anon

ACROSS
1   Leader will let lie (6) WALLOW {Will}{ALLOW}
4   Rare alarm overwhelms Conservative (6) SCARCE {SCAR{C}E}
9   Starts assembling steel in Australian continent (4) ASIA Acrostic
10 Promote one gallery in simplistic surroundings (10) FACILITATE{FACIL{I}{TATE}E} There's an extra E here.
11 Priest holds new weapon (6) CANNON {CAN{N}ON}
12 Mango oil fabricated in Asian country (8) MONGOLIA*

13 Uninitiated, unreserved, unorthodox clergymen (9) REVERENDS uNRESERVED*
15 Wood left in fish (5) BALSA {BA{L}SA}

16 Fat old boy to see, perhaps (5) OBESE {OB}{SEE*}
18 Squats about, Mary Jane first plants (9) DUCKWEEDS {DUCK{WEED}S}

22 Confused bakers in North American state (8) NEBRASKA {N{BAKERS*}A}
23 Flies an irrational number of bundles (6) PILOTS {PI}{LOTS}
25 Bagmen clan cook dessert (10) BLANCMANGE*

26 Waitress amid confusion (4) MAID*
27 Sweats, prays, at last, beheads English rulers (6) SUDORS {p..yS}{tUDORS}
28 Remove regular cleg from Italian dishes with Yoga postures (6) ASANAS lASAgNAS

DOWN
1   Loss was almost on platform (7) WASTAGE {WAs}{STAGE}
2   Train student to make a living (5) LEARN {L}{EARN}
3   Crime of guard (7) OFFENCE {OF}{FENCE}
5   Dependency on large intestine's source of yeast (6) COLONY {COLON}{Ye..t}
6   Share beer on principle (9) RATIONALE {RATION}{ALE}
7   Guards initially missing records (7) ENTRIES sENTRIES
8   Eccentric, our ad-man hacks great Indonesian leader (6,7) ACHMAD SUKARNO*

14 Guarded temple in boundary (9) ENSHRINED {EN{SHRINE}D}
17 Tools for erstwhile British band, we hear (7) BEETLES (~beatles)

19 First off, captain from South has smoked herrings (7) KIPPERS {sKIPPER}{S}

20 Takes ends off of nuts and bolts (7) DETAILS {DE-TAILS}
21 Starting off memoirs about compound (6) ISOMER mEMOIRS*
24 Well-formed endless Manila lagoon (5) LIMAN MANILa*

Reference List

Conservative = C, Gallery = TATE, New = N, Left = L, Irrational Number = PI, Student = L

GRID