Thanks Moley for a Quiptic which serves well as an introduction to cryptics for newer solvers. Definitions are underlined in the clues.
Across
8 Linguist said parrot had good luck (8)
POLYGLOT : Homophone of(said) “Polly”(a common name for a parrot) + G(abbrev. for “good”) + LOT(one’s luck;fortune, good or otherwise).
9 Give in over Christian fast (6)
RELENT : RE(with reference to;about;over, as in “the fight was over a girl”) + LENT(the period preceding Easter observed by Christians by fasting).
10 Smooth and put in order (4)
FILE : Double defn: 1st: …, as with nails, say; and 2nd: …, as with correspondence, say.
11 Obstruction tactic, if burliest characters are drunk (10)
FILIBUSTER : Anagram of(… are drunk) IF BURLIEST.
Defn: …, such as prolonged speaking, to stifle progress in a legislative assembly of, say, the reading of a bill.
12 Deceased student unknown until recently (6)
LATELY : LATE(deceased, as in “the late Mr. So-and-so”) + L(letter displayed on a plate by a learner driver) + Y(symbol in mathematics to denote an unknown quantity).
14 Perhaps let in car carrying instrument (8)
CLARINET : Anagram of(Perhaps) LET IN CAR.
15 I avoided DIY for awful family (7)
DYNASTY : “I” deleted from(avoided)”DIY” plus(for) NASTY(awful;unpleasant).
17 Harass with live blockade (7)
BESIEGE : BE(to live;to exist) + SIEGE(the blockade of a town or building by enemy forces).
Defn: …, as in “the reporters came to besiege her when she arrived at court”).
20 Farm gent made up piece (8)
FRAGMENT : Anagram of(… made up) FARM GENT.
22 Crafty lad gets around Scotsman for a nut (6)
ALMOND : Anagram of(Crafty) LAD containing(gets around) MON(Scottish for “man”).
23 Disagreeable Nana lets up by mistake (10)
UNPLEASANT : Anagram of(… by mistake) NANA LETS UP.
24 Set off in pinstripe (4)
TRIP : Hidden in(in) “pinstripe“.
Defn: …;to trigger, as with a booby trap.
25 EU’s lot managed to make a mess (6)
TOUSLE : Anagram of(… managed) EU’S LOT.
Defn: …, as with a mass of hair.
26 Dispense with outfit uncle got terribly hot in (8)
UNCLOTHE : UNCLE containing(got … in) anagram of(terribly) HOT.
Down
1 A lone hermit (8)
SOLITARY : Double defn: 1st: …, as in “a lone wolf”; and 2nd: A recluse.
2 Use keyboard of a kind (4)
TYPE : Double defn.
3 Hairy fly buzzing round you, say, very loudly (6)
FLUFFY : FLY containing(buzzing round) [ homophone of(…, say) “you“(as used in mobile texting) + FF(abbrev. for “fortissimo”, musical direction to play very loudly) ].
4 New CIA list in emphatic kind of script (7)
ITALICS : Anagram of(New) CIA LIST.
5 Copy book for period in game (8)
CRIBBAGE : CRIB(to copy;to plagiarise) + B(abbrev. for “book”) + AGE(a long period of time).
Defn: … of cards.

6 Timeless style is first model for this artistic movement (10)
CLASSICISM : CLASSIC(in a timeless style, as in “Casablanca is a classic movie”) + IS + 1st letter of(first) “model“.
7 Sun on knees, they say, causes symptom of a cold (6)
SNEEZE : S(abbrev. for “sun”) + homophone of(…, they say) “knees“.
13 Perhaps leaving set with missionary? (10)
EVANGELIST : Anagram of(Perhaps) LEAVING SET.
16 Peg to go on endlessly about each rule, initially for person who’s juvenile (8)
TEENAGER : TEE(a peg;a short pin with a concave head used by golfers) + NAG(to go on endlessly about;to harry someone) + 1st letters, respectively, of(…, initially) “each rule“.
Heard this one?
Tiger Woods drives his BMW into a remote petrol station. As he bends to pick up the nozzle, two tees fell out of his pocket. The station attendant, ignorant of who Tiger is or even of golf, asks him what they are. “They’re tees”. “What are they for?” “They’re for resting my balls when I’m driving.” “Gee, those guys at BMW think of everything!”
18 Shooting at the OK Corral? (8)
GUNFIGHT : Cryptic defn: Reference to the shootout between lawmen and outlaws in Tombstone, Arizona in the American Wild West.
19 Traumatised, with no idea about level (7)
STRATUM : Anagram of(… about) [“Traumatised” minus(with no) “idea” ].
21 Organised party for Frenchman without any particular purpose (6)
RANDOM : RAN(organised, as in “organised a betting pool”) + DO(a party;a social function) plus(for) M(abbrev. for “Monsieur”, a form of address for a Frenchman).
22 Daft tricks seen in cats playing (6)
ANTICS : Anagram of(… playing) IN CATS.
24 Decay after time to move moderately fast (4)
TROT : ROT(to decay) placed after(after) T(abbrev. for “time”).
Thanks both. Quite a lot of anagrams.
[Nice to be reminded of the tees joke, scchua, which I first heard in the 1960s – but it was a Rolls Royce and no Tiger Woods!]
Thanks Moley and scchua
Very nice, but I didn’t see how “carrying” fitted into 14a, or how GUNFIGHT was cryptic at all!
Thanks for the crossword and commentary. 15a doesn’t quite work, does it? If I is replaced by NASTY, you get DNASTYY. “I avoided DIY with awful family” would work better, I think.
I thought 15a was just D[I]Y with the I “avoided” + NASTY.
New for me was CRIB = copy.
Thanks Moley and scchua.
You’re right, Andrew. Apologies to all. Blog corrected.
Andrew @4
I didn’t notice it at the time, but I think Brian has a point. What’s the “for” doing if yours in the parsing?
Thanks to Moley and scchua.
Over at the discussion about today’s Vulcan, some people have been saying that a couple of clues were “barely cryptic”, whereas I thought they were fine. But here, like muffin @2, I’m afraid I can’t see anything remotely cryptic about GUNFIGHT. Are we missing something?
I wondered the same thing about 18d. I assume that Moley intended us to read it in some other way, so that the actual reading would be cryptic, but I can’t see that the intention was.
I suppose the intention of 18d is a vague misdirection in that you might be thinking of filming. But I agree with Lord Jim @8 and muffin @2 that it’s a terribly weak clue which is barely cryptic at all.
And Brian @3 and muffin @7 are right about the parsing of 15, which, like Muffin, I didn’t notice at the time.
But a pleasant enough diversion for a sunny lunchtime.
For 18d, perhaps reading ‘shooting’ as in shooting a film makes it cryptic. There’s an old movie called ‘Gunfight at the O.K. Corral’.
Thanks, Tom @11. I had forgotten the film title. Still think it’s not a marvellous clue, but it does work all right.
muffin @7: Andrew is right in his parsing of DYNASTY and, I think, Brian @3 questions the use of ‘for’ as it is used here.
This particular use of ‘for’ (just meaning ‘+’) is, IMO, rather awful, though others may disagree.
The worst thing is, however, that Moley does it three (!!) times: in 15ac but also in 5d and 21d.
There’s more I do not like very much about Moley’s style (like, for example, ‘first model’ meaning M) but I am happy to leave it there.
An accessible and not too difficult cryptic and so it does fit the bill. Whether this crossword was really well-written is another matter.
muffin@7
Another meaning of “for” would be “presented to”, as in “this is for you”.