No 12126, Monday 02 Oct 2017, Lightning

ACROSS
1   Substitute half of a meal with vegetable (8) SUPPLANT {SUPper}{PLANT}
5   Agreement on a country’s borderline (6) ACCORD {A}{Co...y}{CORD}
9   Discuss one’s electronic essay (8) TREATISE {TREAT}{1'S}{E}
10 Leisurely walk on street with pastry (6) STROLL {ST}{ROLL}
12 Improve breed (5) RAISE [DD]
13 Somehow segregate hidden message (6,3) EASTER EGG*
14 Control rumours about European community (6) DIRECT {DIR{EC}T}
16 Hearing aid’s in demand within hearing distance (7) EARSHOT {EAR'S}{HOT}
19 No second cries let out by hawk (7) TIERCEL {CRIEs+LET}*

21 He spread murmur about priest (6) HELIUM {H{ELI}UM}
23 Last wishes influence mental strength (9) WILLPOWER {WILL}{POWER}
25 Seed — gluten free alternate for smooth transition (5) SEGUE {SeEd+GlUtEn}
26 Put right salesman with attitude (6) REPAIR {REP}{AIR}
27 Coffee say, with breakfast item almost always consumed (8) BEVERAGE {EVER} in {BAGEl}
28 Mum is returning by period of fasting (6) SILENT {IS<=}{LENT}
29 Sues old pal over engagement (8) ESPOUSAL {SUES+O+PAL}*

DOWN
1   Sarcastic writing by nobleman having a bit of temper (6) SATIRE {S{A}{Te...r}IRE}
2   Negotiated epic price drop (9) PRECIPICE*
3   Refreshment in flat terrain (5) LATTE [T]
4   New trail with sodium upfront (7) NASCENT {NA}{SCENT}
6   Spinning car halted at church (9) CATHEDRAL*
7   Australian working with European on layer that protects earth (5) OZONE {OZ}{ON}{E}
8   Representative from Georgia interrupting strike (8) DELEGATE {DELE{GA}TE}
11 Tennis legend smashes records (4) ASHE [T]
15 Save revolutionary leader’s departure (9) EXCEPTION {EXCEPT}{NO1<=}
17 Fragile time machine? (4,5) HOUR GLASS [CD]
18 Attendants braise a rare dish served for starters (8) STEWARDS {STEW}{A}{Rare}{Dish}{Se...d}
20 Order new patch of grass (4) LAWN {LAW}{N}
21 Nearly damage cape with saddle (7) HARNESS {HARm}{NESS}
22 Regularly chew actual grain (6) CEREAL {ChEw}{REAL}
24 Soap finally takes out black mark in part of jacket (5) LAPEL LA(-b+p)PEL
25 Stone thrown by scribe (5) STENO*

GRID