No 12637, Tuesday 28 May 2019, Arden

ACROSS
1   Road transport is slow, 80% will take flight (7) BUSTARD {BUS}{TARDy}

5   Produce milk with hybrid American cattle (7) LACTATE {A+CATTLE}*
9   Old man takes note — it's old fashioned (5) DATED {DA{TE}D}
10 Cavalier's dubious role backing the clique (9) CABALLERO {CABAL}{ROLE*}
11 Soon gets home, rather seriously (9) EARNESTLY {EAR{NEST}LY}
12 Talk about rolling back the tarpaulin a bit (5) PRATE [T<=]
13 House food? (4) DIET [DD]
15 Inertia’s hard to check — greatly affected (8) LETHARGY {LET{H}ARGY*}
18 Live to see the list included in the singing style (3,5) BEL CANTO {BE}{L{CANT}O}
19 One among the internees is a winger (4) ERNE [T]
22 Food for transport, mostly across America (5) SUSHI {S{US}HIp}
24 Dispatched again — almost the entire lot was bitter (9) RESENTFUL {RESENT}{FULl}
26 Malala gets aid, becomes a displaced person (5,4) DALAI LAMA {MALA+AID}*
27 Definite article, perhaps it's to be deleted (5) CLEAR ARtiCLE*
28 Some reportedly pick bird's bone (7) STERNUM {TERN} in {SUM}(~some)
29 She recalled name of rebel (7) HERETIC {HER}{CITE<=}

DOWN
1   Poor state, not many link it with Wisconsin (6) BADGER {BAD}{GERm} (Correction - {BAD}{GERmany} - See comments)

2   Near Tunis it turns dark (9) SATURNINE*
3   Doubled infusion in beer, it will go bad (5) ADDLE {A{DD}LE}
4   Caught in the end — it's essentially single event (9) DECATHLON {DE{C}ATH}{aLONe}
5   Throw next to the entrance (5) LOBBY {LOB}{BY}
6   What ISIS wanted was to bomb the capital within no time (9) CALIPHATE {THE+CAPItAL}*
7   Lords, for example are one up (5) ARENA {ARE}{AN<=}
8   Ran away from French European upbringing (6) ELOPED {DE}{POLE}<=
14 Savoir-faire, here in Paris one's a strategist (9) TACTICIAN {TACT}{ICI}{AN}
16 Prime minister will explain about calories (regular intake) (9) TAOISEACH {T{cAlOrIeS}EACH}
17 Scrape the bottom rung, choose to have fun on the way up (9) GENUFLECT {runG}{E{FUN<=}LECT}
20 Remarks as the team enters (6) ASIDES {A{SIDE}S}
21 Priest is extremely careful with a boy (6) CLERIC {Ca...uL}{ERIC}
23 Comfort as Pound goes into deposit (5) SALVE {SA{L}VE}
24 Reign of the champions, Bill free to leave (5) REALM {REAL Madrid}
25 City by the river is better (5) NICER {NICE}{R}

Reference List
American = A, US,  Note = TE, Hard = H, See = LO, DoubleD = DD, Caught = C, One = AN, Pound = L, Bill = AD, Free = RID, River = R

GRID