Thanks Pan for a typical Quiptic. Definitions are underlined in the clues.
Across
5 Our future king has appropriate headgear (6)
CROWNS : CR(abbrev. for “Charles Rex”, King Charles, our;the crossword setter’s and publisher’s;Great Britain’s future king – who knows if that’s a done deal?) + OWNS(has;possesses).
Defn: … for a monarch.
6 Bears find grass in empty boxes (6)
BREEDS : REED(a tall plant of the grass family) contained in(in) “boxes” minus
its middle letter(empty …).
9 British runners enter these with things to hold up trousers (6)
BRACES : B(abbrev. for “British”) + RACES(events which runners enter in).
Defn: Aka suspenders in the US.

10 Psychological problem developed this year (8)
HYSTERIA : Anagram of(developed) THIS YEAR.
11 Outfit for good listener? (4)
GEAR : G(abbrev. for “good”) + EAR(what’s used for listening).
12 Reflective journalist free to think (10)
DELIBERATE : Reversal of(Reflective) ED(abbrev. for a senior journalist;editor) + LIBERATE(to free from, say, slavery).
13 Mathematician in a casino went bust (5,6)
ISAAC NEWTON : Anagram of(… bust) A CASINO WENT.
18 Observation about retired chap’s loyalty (10)
COMMITMENT : COMMENT(an observation;a remark) containing(about) reversal of(retired) TIM(a chap’s name).
21 Adolescent involved in chaste encounter (4)
TEEN : Hidden in(involved in) “chaste encounter“.
22 Londoners without new translation for medieval language (3,5)
OLD NORSE : Anagram of(… translation) [ “Londoners” minus(without) “n”(abbrev. for “new”) ].
23 Cut of meat popular with composer (6)
CHOPIN : CHOP(a cut of meat, as in a “pork chop”) + IN(popular;in fashion).
24 Beat patient’s last hospital-acquired infection (6)
THRASH : Last letter of(…’s last) “patient” + H(abbrev. for “hospital”) + RASH(an acquired infection affecting the skin).
25 Sketch is badly singed (6)
DESIGN : Anagram of(badly) SINGED.
Down
1 Is relevant to arguments against covering nuclear research facility (8)
CONCERNS : CONS(arguments against, in contrast to “pros”) containing(covering) CERN(acronym for “Conseil européen pour la recherche nucléaire”, the laboratory;research facility of the European Organisation for Nuclear Research).
2 American embraced by dancing nude virgin (6)
UNUSED : US(abbrev. for “United States”, used to refer to things American) contained in(embraced by) anagram of(dancing) NUDE.
3 Angry lad almost gets wife’s weapon (8)
CROSSBOW : CROSS(angry) + “boy”(a lad;a youngster) minus its last letter(almost) plus(gets) W(abbrev. for “wife”).
4 Came into contact with source of earthly or heavenly body (6)
METEOR : MET(came into contact with) + 1st letter of(source of)” earthly” + OR.
5 Canine’s first sign of tooth decay (6)
CARIES : 1st letter of(…’s first) “Canine” + ARIES(an astrological sign).
7 Religion contributing to clash in Tokyo (6)
SHINTO : Hidden in(contributing to) “clash in Tokyo“.

8 One with an eye for the ladies has letter delivered to country with two queens (11)
PHILANDERER : PHI(a letter in the Greek alphabet) plus(delivered to) LAND(a country) plus(with) ER,ER(abbrev. for “Elizabeth Regina”, the Queen x 2).
14 With training, skater is a star (8)
ASTERISK : Anagram of(With training) SKATER IS.
15 Brace used to help the spine, when oxygen is in short supply (8)
ORTHOSIS : O(symbol for the element, oxygen) + anagram of(… supply;in a supple way, similar to “humbly”) [IS contained in(in) SHORT].
I’m not satisfied with the explanation of “in”.

16 Work hard for alien’s convenience (6)
TOILET : TOIL(to work hard) plus(for) ET(abbrev. for “extraterrestrial”;an alien).
17 Germ primarily found in West African country is not life threatening (6)
BENIGN : 1st letter of(… primarily) “Germ ” contained in(found in) BENIN(a West African country).
19 Staff on time to meet artist producing sacred text (6)
MANTRA : MAN(to staff;to fill an organisation with employees) placed above(on, in a down clue) plus(to meet) RA(abbrev. for a member of the Royal Academy of Arts;an artist).
Defn: … a word (or sound) in Hinduism and Buddhism, that’s repeated during meditation.
20 Pass mark given to English student at last (6)
TICKET : TICK(a mark;a symbol indicating something is correct or accepted) plus(given to) E(abbrev. for “English”) + last letter of(… at last) “student“.
Perfect companion to Nutmeg.
Thanks Pan and scchua
Mostly fine, but I wouldn’t expect to come across a word I didn’t know in a Quiptic. (It was ORTHOSIS, and I needed a wordsearch.)
Pretty good Quiptic, although like muffin I didn’t know ORTHOSIS (thank goodness, in a way)
Re 5a: It is possible that, if he does take over the business one day, Chas might call himself George VII (one of his other names). Or even King Philip. Or even King Arthur. Imagine that!
Thanks scchua and Pan. this was mostly perfectly suited to the quiptic spot, though I, too had trouble with ORTHOSIS, which I’d never heard of – the first part was quite obvious, but I had to look up the ending, not helped by the unusual parsing, which I think is O+IS, with *SHORT inside. The unexpected word order is necessary for the surface.
Of course, I may be wrng.
wrong
I completed this in record time, for me, which admittedly is not saying much (& compared with the speed and mental agility of FS regulars, is still laughably slow) but nevertheless I’m now feeling very pleased with myself.
Although the crosses and the clue meant 15D had to be Orthosis, I’d never heard of it either – but then I frequently learn new words via the Grauniad’s crosswords, so par for the course there.
Speaking personally, I’m never wild about clues where an arbitrary name is clued as girl/boy/woman/man, so I winced at the Tim part of Commitment – but on the other hand, I really enjoyed Isaac Newton, Concerns and Toilet.
Thanks to Pan and Scchua
PS Shirl, you’re quite right: there’s no reason to suppose he’ll become Charles III, when/if he gets the job. One of his recent predecessors was actually called David, but became a George when he was king. I’m no monarchist (perish the thought!) but I remember reading somewhere that they can pretty much name themselves whatever they want. Within reason – which, alas, probably rules out Slartibartfast….
Thank you Scchua and Pan.
Re ORTHOSIS, I parsed it as ORTH -OSI- S, ie SHORT* on the outside, which explains the “in”, I think.
il principe dell’oscurità@7.
Re 15d, yes, I thought of that too, but that’s just as unsatisfactory, since it’s “O(xygen) is”, and not “O(xygen) si” in the clue.
Could not the O IS be put in SHORT and then the whole lot be treated “supply”?
I would stretch to my last offering for the sake of the great surface.
Useless information time. Wellbeck @ 6 … this may be revealing more knowledge of the royal family than I might like to admit to, but I think Edward VIII was known in his family as David whereas George VI was known as Bertie (as confirmed by the respective Wikipedia entries).
Thanks to Pan; and to scchua – your photos are always a welcome addition to the blog. I liked the braces!
Thanks for the correction, anotherAndrew! Not being a royalist, my knowledge of the minutiae is sketchy – but I was wanting to agree with Shirl in principle. And, like Shirl, I find the idea of a King Arthur rather enchanting…
Fine Quiptic (Pan is one of the better setters at this level).
I had no problem with 15d (yet, had to think about it). I cannot be anything else than il principe etc suggested @9 [that said, it could either be O+(IS inside SHORT)* or (O+IS, together inside SHORT)* – doesn’t make much difference].
I am not convinced by Pan using ‘acquired’ in 24ac and that use (again) of ‘for’ in 16d, don’t start me talking!
Altogether, all very nice and smooth.
Many thanks scchua & Pan.
ps, what Stella said @4: The unexpected word order is necessary for the surface, is just so wrong (but Stella, I don’t put the blame on you for saying this 🙂 ). (Almost) nothing is necessary for the surface, the surface should never take over!
Oh, and by the way, these bears in 6ac were quite clever, weren’t they?
Finding grass in boxes that were empty ….
Sil@13,
My discomfort (dissatisfaction is perhaps too strong a word) is with having an operation (specified by the containment indicator “in”) only to be undone by another operation (specified by the anagram indicator, “supply”). As with economy with (or nonsuperfluity of) words in the clue, I expected the same with parsing of the solution.