No 12449, Wednesday 17 Oct 2018, Arden

ACROSS
6   Marked out, first man goes for duck (5) DRAKE mARKED*
7   Directions to reach the top, coined first in 1984 (8) NEWSPEAK {N}{E}{W}{S}{PEAK}
10 Conductors for current carrying master switch (7) MAESTRI {AMSTER*}{I}
11 On an average can do the account (7) PARABLE {PAR}{ABLE}
12 Blockade — only master on freighter can change sides (7) EMBARGO {(+e)E{M}BARG(-e)}O O from? (Addendum - {O}{M}{BARGE} to  {E}{M}{BARG}{O}- See comments)
13 Staff have a point; Peter Principle basically works (7) SCEPTRE {S}{PETER+prinCiple}*
14 Moving south? Beware of one's location (11) WHEREABOUTS*
19 Not even once add something extra — figure that! (7) OCTAGON {OnCe}{TAG ON}
21 Out LBW, go on find a weapon (7) LONGBOW*
23 Positive attitude? Sure, open to openness (7) CANDOUR {CAN DO}{sURe}
25 Record — list prepared to the last letter (7) EPISTLE {EP}{LIST*}{thE}
26 Scientist finds a way to check designs at regular intervals on both sides (8) EINSTEIN {dEsIgNs}{ST}{dEsIgNs}
27 Electronic instrument will wash (5) ELUTE {E}{LUTE}

DOWN
1   What Cupid does to acknowledge cheers (4,1,3) TAKE A BOW [DD]
2   Way to break free, free of rot (6) FESTER {FE{ST}ER*}
3   Painted on a building on the other side of the world (10) ANTIPODEAN*
4   Hands go up in exchange (4) SWAP<=
5   Stop over for a little chat (6) RABBIT {BAR<=}{BIT}
6   The French are crazy over a young woman (6) DAMSEL {LES}{MAD}<=
8   Substandard location in short for an arriviste (7) PARVENU {PAR}{VENUe}
9   Soldiers wearing tote cap (5) BERET {BE{RE}T}
13 They are commissioned to lift vehicle, change directions later (10) SUBALTERNS {BUS<=}{ALTER}{N}{S}
15 Put pen to paper, no pressure, so plunge right in (7) ENGROSS {pEN}{GROSS}
16 He wrecks boats at sea on the way up (8) SABOTEUR {BOATS*}{RUE<=}
17 It's very painful reaction, I can guarantee (5) VOUCH {V}{OUCH}
18 Starts taking wickets with ease reportedly — pluck them out (6) TWEEZE {Ta...g}{Wi...s}{EEZE}(~ease)
20 Girl comes into money, it's used in leather industry (6) TANNIN {T{ANN}IN}
22 Fixed one up, one went ahead (6) NAILED {AN<=}{1}{LED}
24 Free to untangle the knot (4) REEF*

GRID