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An interesting puzzle, I found it easier to guess the solutions than to parse them. Thank you Basilisk.
There is some amusing elision going on in the grid: REVISED VERSION, STAINLESS STEEL etc. I guess the number of these depends on how amused you are prepared to get. VENUS UNDERWEAR and VIOLATING TUNIC capture my imagination and NASALLY HOLSTER sounds painful but a definite possibility.
I will be away for most of the day, if you spot a problem leave a comment and I will update the post later.

| ACROSS | ||
| 1 | REVISED | Studied for exams in a new form (7) |
| double definition | ||
| 5 | VERSION | Dislike expurgating article in translation (7) |
| aVERSION (dislike) missing (expurgating) A (indefinite article) | ||
| 9 | PHOTO | Contents of portfolio updated with recently taken picture (5) |
| PortfoliO with middle letters (contents) replaced by HOT (recently taken, stolen) | ||
| 10 | SYNTHESIS | What conflates reporter’s offence with aspiring doctor’s work? (9) |
| SYN sounds like (reporter’s) SIN with THESIS (aspiring doctor’s work, for a PhD) | ||
| 11 | STAINLESS | Lacking evidence of guilt, let heartless assassin off (9) |
| anagram (off) of LET and ASSasSIN (heartless) | ||
| 12 | STEEL | True Grit is appropriate for audience (5) |
| sounds like (for audience) “steal” (appropriate) | ||
| 13 | ELIDE | Top parts exhausted ensemble leave out (5) |
| LID (top) inside (parts) EnsemblE (exhausted, no middle) | ||
| 15 | AMUSINGLY | Entire range unveiled one by one in delightful fashion (9) |
| gAMUt (entire range) missing outer letters (unveiled) then SINGLY (one by one) | ||
| 18 | SIGHT-READ | Sound unhappy having step to perform with no preparation (5-4) |
| SIGH (sound unhappy) with TREAD (step) | ||
| 19 | GULCH | Pass for American university lecturer visiting government agency briefly (5) |
| U (university) L (lecturer) inside (visiting) GCHQ (government agency, briefly=shortened) | ||
| 21 | EXTRA | More extensive period covers unknown time (5) |
| ERA (period) contains (covers) X (an unknown) T (time) | ||
| 23 | PAROCHIAL | “Narrow-minded and racial” leaders of Houses of Parliament must change (9) |
| anagram (must change) of RACIAL with first letters (leaders) of Houses Of Parliament | ||
| 25 | SENSITIVE | Even so, to begin with it is surprisingly controversial (9) |
| anagram (surprisingly) of EVEN So (first letter, to begin with) and IT IS | ||
| 26 | PLANT | Agent works to introduce growth (5) |
| quadruple definition | ||
| 27 | NUCLEAR | Form of power using uranium introduced by new patent (7) |
| U (Uranium) inside (introduced by) N (new) CLEAR (patent) | ||
| 28 | REACTOR | Person who responds roughly to stern nurses (7) |
| C (circa, roughly) TO inside (…nurses) REAR (stern) | ||
| DOWN | ||
| 1 | RIPOSTE | Is poet right to disseminate combative response? (7) |
| anagram (to disseminate) of IS POET R (right) | ||
| 2 | VIOLATING | Interfering with instrument can start to grate (9) |
| VIOLA (instrument) TIN (can) then Grate (first letter, start to) | ||
| 3 | SWOON | Faint edges of shadow obscuring front of satellite (5) |
| ShadoW (edges of) and mOON (satellite) missing (obscuring) front letter | ||
| 4 | DESPERATE | Hopeless judge is behind reclassification of speed (9) |
| RATE (judge) follows anagram (reclassification) of SPEED | ||
| 5 | VENUS | Places overlooking Earth and its neighbour (5) |
| VENUeS (places) missing E (Earth) | ||
| 6 | REHASHING | Drug given to control group initially producing minor changes (9) |
| HASH (a drug) inside (given to) REIN (control) Group (initial letter of) | ||
| 7 | ISSUE | Make claim to support one’s point (5) |
| SUE (make claim to) following (to support) I’S (one’s) | ||
| 8 | NASALLY | Sneaks regularly associate in a nosy way (7) |
| every other letter (regularly) of sNeAkS then ALLY (associate) | ||
| 14 | ESTUARINE | Meandering river and sea unite in this way (9) |
| anagram (meandering) of R (river) and SEA UNITE – they way a river and sea unites | ||
| 16 | UNDERWEAR | Layer beneath surface subjected to erosion (9) |
| UNDER (beneath surface) with (subject to) WEAR (erosion) | ||
| 17 | GALLIVANT | Terrible man pursuing everybody welcomed by great flirt (9) |
| IVAN (terrible man, Ivan the Terrible) following ALL inside (welcomed by) GR (great) | ||
| 18 | STEPSON | Suppresses minor feature of new relationship? (7) |
| STEPS ON (suppresses) | ||
| 20 | HOLSTER | Where one might find piece about revolutionary by British composer (7) |
| RE (about) reversed (revolutionary) following (by) HOLST (British composer) – a piece is a gun | ||
| 22 | TUNIC | Turn up wearing slashed trousers and jacket (5) |
| IN (wearing) inside (…trousers, pockets) CUT (slashed) all reversed (turn up) | ||
| 23 | PRIOR | Religious person asking personal questions on the phone (5) |
| PRIOR sounds like (on the phone) “prier” (one – a religious person – who asks personal questions) | ||
| 24 | COPRA | Company revealed jet’s source of oil (5) |
| CO (company) then sPRAy (jet) missing outer letters (revealed, exposed) | ||
I’d already done battle with Basilisk’s alter ego before I started this one which certainly helped to get on the setter’s wavelength
Lots to enjoy – I did like the quadruple definition 26a amongst many others
Thanks to Basilisk and PeeDee
Very chewy but satisfying grid from Basilisk.
Can’t claim to have completed this without cheats but there was much to enjoy from individual clues such as GULCH, HOLSTER and GALLIVANT to the wonderful pairings spotted too late in the game to help much.
I had ‘stentor’ for 28a at first but it wouldn’t chime with 16d and 24d and then along came NUCLEAR, thankfully.
Is the definition for GULCH (19a) not just ‘pass’ (as in ravine, valley)?
Thanks to Basilisk for another highly entertaining workout and to PeeDee for a much-needed blog.
I liked doing battle with Basilisk today. Seeing the across word pairs helped with a few near the top of the grid and REACTOR towards the end. I took a while to see what AMU… was doing in 15a, but despite exactly the same trick, missed the derivation of the …PRA bit of 24d.
I liked the quadruple def for PLANT and the “Wild West” crossing of GULCH and HOLSTER.
Thanks to Basilisk and PeeDee
Just popped across from the Indy (well it isn’t up yet) to compliment Basilisk on a tremendous puzzle today and, particularly, on ESTUARINE: as superb a melange of definition, wordplay and relevant surface as I’ve seen in a long time. Unfortunately a DNF as I bunged in the unparsed ELITE (top/top parts) for 13 ac.
crypticsue @1 refers to Basilisk’s alter ego. The Setters list mentions Serpent in the Indy – but today it’s Alchemi. Does Basilisk set for another publication as well?
Thanks to Basilisk and PeeDee. (I’m undecided between SENSITIVE UNDERWEAR and STAINLESS UNDERWEAR)
Great puzzle. Love PHOTO SYNTHESIS sitting alongside with each other.
Very classy.Many thanks JC and PeeDee
Postmark@4 He’s today’s Telegraph Toughie setter
crypticsue @6 Thank you.
Had ‘stentor’ at 28 like Diane @2 but unlike her didn’t persevere, so a DNF for me today. Shame, it was a corker.
Thanks to both.
All done and all parsed but it took me a while and I needed a word wizard. I’ve seen Basilisk do the paired across solutions before, but once I got the top three I was expecting all the others to be pairs.
Sight-read was new to me.
Thanks JC and PeeDee.
Hi Diane, I think “for American” in the definition indicates that GULCH is US English rather than British English
DNF as I had SNOTTER at 28ac(*to stern) and a SNOTTER actually responds roughly! Also failed at 16d with UNDERSEAS as a result. Thanks setter and blogger.
Thanks to PeeDee and Basilisk
I had the def in 21a as simply “more”
and in 16d “layer beneath surface”
All done and dusted except for spotting the pairs. We should have realised something was afoot with this setter.
Thanks, Basilisk and PeeDee.
Many thanks to PeeDee for the great blog and to everyone who has been kind enough to leave a comment.
Dansar@12 has identified the intended definitions in 21a and 16d.
Thanks Basilisk and PeeDee
A DNF for me by putting in a slack and unparsed ELITE at 13a. A really neat and challenging puzzle where I also missed the proper parsing of GULCH, having not heard of the GCHQ organisation and not seeing the linked pairs of across clues. Was happy to get the rest out after taking about twice the average time to get it finished.
A lot of tweaking by removing letters from word play words under different guises and a lot of very subtle definitions of the key word and bits of the word play. Getting the anagram fodder for SENSITIVE was pretty tricky.
Finished in the SW corner with that SENSITIVE, SIGHT-READ (a new term) and ESTUARINE (where I used a word finder ‘cos my brain was puffed out by that time).
Clever and amusing surfaces in the clues, something I very much admire. Thanks for an enjoyable puzzle and blog.