No 12122, Tuesday 26 Sep 2017 Arden

ACROSS
1   Crafty bird takes measure to go sub-sonic (13) MACHIAVELLIAN {MACH 1}{AV{ELL}IAN}
10 Stuck in traffic, I'm so upset over smell (5) OSMIC [T<=]
11 Likely top line at random (9) POTENTIAL*
12 Dog crosses river, one to capture the moment (3,6) BOX CAMERA {BOX{CAM}ER}{A}

13 After greeting, poke under cover (5) HIJAB {HI}{JAB}
14 Period when one's not big-hearted (7) S?S?O?E (Addendum - SYSTOLE [CD] - See comments)
16 Setter had managed to get power tool (7) GRAPNEL {RA{P}N} in {GEL}
18 Ex-British PM's day out with Netanyahu, say (7) ISRAELI dISRAELI
20 A few have another name, tails clipped in the country (7) SOMALIA {SOMe}{ALIAs}

22 Seats distributed according to what one has (5) ASSET*
24 Demand for boy to get into mutual arrangement (9) ULTIMATUM {TIM} in {MUTUAL}*
26 It's largely an assembly on the voice box (9) LARYNGEAL {LARGELY+AN}*
27 High rent all around, it pricks (5) THORN {TORN} over {H}
28 Power behind the throne, Cardinal will revolt after midnight (8,5) EMINENCE GRISE {EMINENCE} {niGht}{RISE}

DOWN
2    Combines runs — made six (7) ADMIXES*
3    Stable gear — cut a little extra (9) HACKAMORE {HACK}{A}{MORE}

4    Enough help making it go up a bit (5) AMPLE [T<=]
5    Alienates sergeant's order (9) ESTRANGES*
6    Change at the top, group gets a meal (5) LUNCH (-b+l)LUNCH
7    A month to accept offer — capital! (7) ABIDJAN {A}{BID}{JAN} This id the economic capital of Ivory Coat or Cote D'Ivoire
8    Pompously it's rejected, call placed in Mumbai once (13) BOMBASTICALLY {ITS<=}{CALL} in {BOMBAY}
9    WW III? China is a threat to the world (6,7) GLOBAL WARMING {GLOBAL} {WAR}{MING} What's the role of III?
15 Colossal gain finally — fertiliser input is unrestrained (9) EPICUREAN {EPIC}{UREA}{gaiN}
17 Change over — uncle in Chennai's from old school (4,5) ALMA MATER {AL{MAMA}TER}
19 After meat and drink, a deserted platform (7) ROSTRUM {ROaST}{RUM}
21 Applications — only time pride is dented (7) LOTIONS {O}{T} in {LIONS}
23 Famous address in and out of joint (5) TENON {TEN}ON Anno pending 
25 Character detained inside until departure (5) TILDE [T]

GRID