And some very lovely wordplay there is herein too – I was particularly fond of a few of the down clues. Honourable mentions to “chill out, brah!” and the off-the-wall madness of YURT/YUFT, but the biggest smile was raised by 3dn managing to hide such a long word in a philanthropist and an ostrich. Another really good puzzle – much admiration to the brilliant setter!
ACROSS
1 Discarded bits of gold line considered magical reflected American vanities (6-4)
YELLOW-BOYS: reversed LEY [line considered magical] + LOWBOYS [American vanities]
An obsolete word for gold coins, hence the “discarded”. Lowboys are short-legged American dressing tables with drawers, apparently.
6 Must for fermenting? (4)
STUM – (MUST*) [“for fermenting”], &lit, as stum is pretty much the same thing as must, unfermented grape juice.
9 Ruddy six-footer as Walloon’s rival? (10)
FLAMINGANT – FLAMING ANT [ruddy | six-footer]. A Flemish nationalist, hence no friend to Wallonia.
10 Prisoner releases a one-pound rodent (4)
JIRD – J{ailb}IRD [prisoner, minus A 1 LB]. A jird is some kind of Berber gerbil.
12 Intensity of warmth, both reduced by flapping true spotted cloth (7,7)
HEATHER MIXTURE – HEA{t} THERMI{c} [intensity | of warmth, “both reduced”] + X [by] + (TRUE*) [“flapping”]. A woolen fabric speckled like heather.
14 I repair junk: I live in Philippine mountains (6)
IGOROT – I GO ROT [I | repair | junk]. A Filipino ethnic group inhabiting the mountains of Luzon.
15 Proper lives led by instant messaging in the first place (8)
IMPRIMIS – PRIM IS [proper | lives] “led by” IM [instant messaging]
17 Reluctant to wear headless dummy’s strip (8)
UNCLOTHE – LOTH [reluctant] to wear {d}UNCE [“headless” dummy]
19 Aberdeen’s distant: return its grant to stop minor injury (6)
ABEIGH – reverse GIE [(Scottish word for) grant] inside ABH [minor injury (as opposed to GBH)] to get a Scots (Aberdeen’s) word for aloof.
22 Violent bishop accepted by God passed easily in America, having leather straps (14)
THOROUGHBRACED – ROUGH B [violent | bishop] “accepted by” THOR [God] + ACED [passed easily (as in a test), in America]
24 Christian soldier statues were buried here in China (4)
XIAN – double def. Xi’an, home of the famous Terracotta Army.
25 Tricky to read clue free of impurities amenable to solution (10)
EDULCORATE – (TO READ CLUE*) [“tricky”]. Means “to free from soluble particles by washing”.
26 Reminder that there’s potassium in long green fruit (4)
CUKE – CUE [reminder] that there’s K [potassium] in
27 I deeply lament abuse about climate indicators (10)
ISOCRYMALS – I SO CRY [I | deeply | lament] + reversed SLAM [abuse]. An isocryme or -crymal is “a line connecting points on the Earth’s surface having the same mean temperature in the coldest month of the year.”
DOWN
1 Birchbark-oiled leather tent of Siberia with right side cut
off almost-lowest part? (4)
YUFT – YURT is the tent of Siberia, find its penultimate letter (“almost-lowest part”) and cut the right side off so that an R becomes an F. Yuft is Russian leather, I’ll take the birchbark-oiled bit on faith.
2 Release Australian plant-eater south of grassland (5,2)
LEAVE GO – VEGO [Australian plant-eater: the equivalent of a “veggie” here I assume?] south of LEA [grassland]
3 “Overarching” philanthropist hot on ostrich cages (12)
OPISTHOTONOS – impressive hidden (“caged”) in {philanthr}OPIST HOT ON OS{trich}
4 Minor software problem that produces shrill reports? (6)
BUGLET – if a BUG is a software problem then a BUGLET could be a minor one of those. Or else it’s, as you might guess, a small bugle.
5 One has permission to set about guenon monkey raised for forest-dwellers (8)
YANOMAMI – I MAY [one has permission] set about MONA [guenon monkey], all reversed for the traditionalist Amazon tribespeople that there were lots of films and documentaries about in the 1980s.
7 Bring up half-forgotten Hawaiian dress scandal a few days before a feast (7)
TRIDUUM – MUU-{muu} DIRT [“half-forgotten” Hawaiian dress | scandal], all reversed. A period of prayer or religious celebration lasting three days.
8 Recall Noah’s son, mostly groomed within religious schools (10)
MEDRESSEHS – reversed SHEM [Noah’s son], DRESSE{d} [“mostly” groomed] within. Fortunately the wordplay sorts out the vowels for you as otherwise they could all equally be A’s.
11 Once reproachful former right-winger gathering for support? (12)
EXPROBRATORY – EX TORY [former | right-winger] “gathering” PRO BRA [for | support].
13 Poisonous smoke with auto fouled by internal combustion (10)
CIGUATOXIC – CIG [smoke] with (AUTO*) [“fouled”] + X IC [by | internal combustion]
16 Object for lawyers is to protect witch and plug cracks in one’s case? (8)
RHAGADES – RES [object, for lawyers] “protects” HAG AD [witch + plug]. Rhagades are cracks or fissures in the skin.
18 Stick with bent head master in jug? (7)
CROMACK – MA [master] in CROCK [jug]
20 US president more than half crazy, exhibiting array of bloomers (7)
IKEBANA – IKE [US president (Eisenhower)] + BANA{nas} [“more then half” crazy]
21 Crippled by indecision, regularly ignored and upset: chill out, brah! (6)
ABULIC – every other letter of C{h}I{l}L {o}U{t} B{r}A{h}, in reverse
23 Catfish killed when coming from the bottom (4)
WELS – reversed SLEW [killed]
Edited at 2019-01-02 08:30 am (UTC)
Drat.