The instructions started out clear, and conventional enough, but became rather more cryptic:
In six of the across and seven of the down clues, a word connected to an unclued entry must be removed. All other clues contain an extra letter; these indicate a framework. Only seven other cells obey the rules of the framework and provide the keys needed for the 15ac 30ac 7d. Thanks for playing.
This was a puzzle in three stages for me: stage 1, solving the clues without worrying too much about identifying the extra words and letters; stage 2, working out the parsing in detail; and stage 3, discovering the SOAP OPERA THEME, as announced in the unclued 15 and 30 across, and 7 down.
Having guessed SOAP and OPERA for the unclued answers, I noticed that the extra words in the acrosses – glass, sugar, saddle, soft, hard and yellow – are all types of SOAP; in the downs, grand, light, space, horse, folk, ballad and comic are type of OPERA.
The extra letters spell out FIRST ROW AND COLUMN. In the first row we see STAVE, and in the first column, reading up, EGBDF, which are the notes on the line of a musical stave (with a treble clef). I learned these from the mnemonic Every Good Boy Deserves Favour, but other versions are available. So the THEME is a musical one. The “seven other cells [that] obey the rules of the framework” are those where the letter matches the note name corresponding to the position on the stave. These are highlighted in pink in the diagram, and they give the beginning of the THEME tune of the SOAP OPERA EastEnders (explaining “thanks for playing”), shown in more conventional notation here:

Remarkably, as well as showing the pitches, Glyph has show their durations, with the initial C D E F being in consecutive columns, and the final G A F spread out to match the rhythm.
In the clues below the extra words/letters are highlighted thus.
| Across | ||||||||
| 6 | ILEUM | Part of system ruining life with little hesitation (5) LIFE* + UM |
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| 7 | THINNER | Glass less sturdy and not all there hotel admitted (7) INN in THER[e] |
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| 9 | FEARSOME | Frightful fellow gets paid in East London (8) F + EARNS + [h]OME (pad) |
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| 11 | DAHLIA | ‘Sugar flower had turned’, Glyph put in note (6) Reverse of HAD + I (Glyph – the setter) in LA |
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| 12 | DOWN‑AT‑HEEL | Shabby looking saddle – he won’t deal with repairs (4-2-4) (HE WON’T DEAL) |
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| 15 | SOAP | (unclued) | ||||||
| 16 | BREAK-UP | End relationship as one spewing about American bastard turning soft (5-2) Reverse of A in PUKER + B (bastard, euphemistically). I would prefer this without a hyphen for the verbal usage |
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| 18 | TOWARDS | Almost falling back, drunk inspiring doodler (7) Reverse of DRAW (doodle) in SOT |
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| 20 | GUSH | Go on! Finish off Magnums, say, with Mum (4) GU[n] (e.g. a Magnum) + SH (quiet, mum). I original had a semi-unparsed MUSH here, as a “go on!” to sledge dogs, which caused me some problems in seeing what was going on in the first column |
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| 22 | AGRONOMICS | Posting amigo’s corn for rural research (10) (AMIGO’S CORN)*, with “posing” as the anagram indicator |
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| 25 | EARNER | Aristocrat and techie both fall short finding source of hard profit (6) EAR[L] + NER[D] |
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| 26 | AGITPROP | For pro-communist publicity, race US soldier first to the pole (8) A (ace) + GI + T[he] + PROP (pole) |
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| 29 | ICE FISH | Island chef is cooking yellow seafood (3,4) I[sland] + (CHEF IS)* |
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| 30 | OPERA | (unclued) | ||||||
| Down | ||||||||
| 1 | SIDE DOOR | Audibly expressed frustration, cross about grand entrance, not so grand (4,4) Homophone of “sighed” + reverse of ROOD (cross) |
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| 2 | TEAR | Drop stage light in delivery (4) Homophone of “tier” (stage) |
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| 3 | AMMO | Shot part of Space Jam movie (4) Hidden in jAM MOvie |
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| 4 | VINDALOO | Meal soon returned, duck overwhelmed by sauce (8) Reverse of LAD (son) + O (duck) in VINO (sauce) |
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| 5 | ENTHUSIASM | Broken horse has minutes to find spirit (10) (HAS MINUTES)* |
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| 7 | THEME | Top two in team bagging wedge for topic (5) HEM (edge) in TE[am] |
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| 8 | RAITA | Dish from Indiana and Arkansas served up containing first-rate bit of tenderloin (5) A1 T[enderloin] in reverse of AR[kansas] |
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| 10 | SPA | Somewhere to relax essential to newspaper folk (3) Hidden in newSPAper |
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| 13 | NEAT-HANDED | Close to salvation, Dante frolicking around edges of hellhole – skillful! (4-6) [salvatio]N + H AND E (the “edges” of hellhole) in DA[N]TE* |
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| 14 | HOP | Endlessly desired spring (3) HOP[e] (desire) |
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| 17 | UNAFRAID | Brave peacekeepers cease supporting half of Africa (8) UN (United Nations, peacekeepers) +AFR + AID (ease) |
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| 18 | TAO | Way out in Asia, stay good at heart (3) [s]TA[y] [g]OO[d] |
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| 19 | DOCTORAL | Partly reduced budget – university cancelled exam relating to certain degrees (8) DO (party) + CUT (budget) less U + ORAL |
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| 21 | UMAMI | Flavour our Gallic friend bolsters using mushrooms initially (5) U[sing] M[ushrooms] + AMI (French “friend”) |
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| 23 | REACH | Get to march for Reform around centre of Bournemouth (5) [Bourn]E[mouth] in MARCH* |
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| 24 | OFT | Ballad poet’s frequently using expression of wonder on paper (3) O! + FT |
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| 27 | ICON | None admired his nude study (4) [h]I[s] + CON (to study) |
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| 28 | PIER | Comic Morgan’s unfinished column (4) PIER[S] (P Morgan, journalist and commentator) |
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Thanks Andrew and Glyph.
I looked for 15a, 30a found them unclued, but 7d was clued – ‘theme’ was the solution, my FOI.
I had the words connected to SOAP, OPERA and, FIRST ROW AND COLUMN by Monday evening, and was stuck.
I realized that it is music related; without subject knowledge could not proceed.
Then an expert solver said that the letters F D B G E are not gibberish, and suggested that I recall a childhood mnemonic which has “fruit” in it. He was referring to normal middle/upper class childhood in UK.
Any way, I found ‘Every Good Boy Deserves Fruit’; ‘All Cows Eat Grass’ etc and delved into Theory of Music….
My 12-year old grandson looked at the completed grid, and saw, C D E F G A F (another expert solver had confirmed 4 and 7 are the same key).
He played it on his piano.
Google AI suggested that it could be Nadia’s Theme in the Young and the Restless. We listened to it, and my grandson disagreed. For some reason he looked at EAST LONDON in 9a asked me about it; I assured him that had nothing to do with what we are trying to do. Then I suddenly remembered EastEnders and we played its theme. My grandson confirmed it – 100%.
Google AI apologized for the error, and offered some explanation, but we were sure it was EastEnders.
I have promised to share the prize with my grandson if we win it.
Great setting. Thanks again.