Some clues with multiple letters and extra letters in the wordplay of other clues. An unclued entry and then shade three blocks of letters to illustrate the theme. Intriguing.
The multiple letters in cells I lucked upon quite early and my assumption proved to be a good one. They were all RED.
The unclued entry fell next and required some googling to confirm his area of expertise. WILLIAM MORRIS
The additional letters spell out DRAW V(five) STRAIGHT LINES FILL SHAPE CREATED
The 13 cells being ARTS AND CRAFTS symbolically making a door and windows in the RED HOUSE formed by linking all the cells with RED in them. https://en.wikipedia.org/wiki/Red_House,_Bexleyheath. My artistic representation below.
Many thanks Vismut – pretty accessible puzzle, a pleasing ending and educational too
Key: * anagram; DD double definition; underline definition; Rev reversed
| Across | |
| 1 100,000 nuts (6) | |
| D | c(100) + 000 (duck + o + o) = CUCKOO |
| 5 Makes fresh plans for earl engaged in dressing up (7) | |
| (e + dressing)* = REDESIGNS | |
| 11 New country leaderless for a short time (6) | |
| R | raw (new) + chile (country) = c (leaderless) = AWHILE |
| 12 Televise short race in southern Norway (6) | |
| A | career(race) – r in s (south) + N (Norway) = SCREEN |
| 13 Cut lawn and tree species of ancient man (10) | |
| W | (lawn + and + tree)* = NEANDERTAL |
| 14 Finish selling (6) | |
| V | DD ENDING |
| 15 Start to make teas brewed from this? (4) | |
| S | m (start to make) + (teas)* = MATE |
| 16 Frame carted about (4) | |
| (carted)* = REDACT | |
| 19 Jogged bottle of Parisienne sent back to the rear (6) | |
| decanter (bottle) moving de (of Parisienne) = CANTERED | |
| 21 Grain money cheque originally ripped (9) | |
| T | bread(money) + c(cheque originally) + torn (ripped) = BREADCORN |
| 26 I roll into pub after soldiers to get round (9) | |
| R | or (soldiers) + i + curl(roll) in bar (pub) ORBICULAR |
| 30 Fixed look from one celebrity accompanying important date (6) | |
| A | star (celebrity) + era (important date) = STARER |
| 33 Load of herring caught by bucket (4) | |
| I | c(caught) + rain (bucket) = CRAN |
| 34 Clips chartered surveyor fencing lane (4) | |
| G | cs (chartered surveyor) around gut (lane) = CUTS |
| 35 Works hard, hollow grinder handles (6) | |
| H | gr (hollow grinder) + hafts (handles) = GRAFTS |
| 37 Woman eating at 12 runs out for plum (10) | |
| T | dame (woman) around at screen – r (runs) = DAMASCEENE |
| 38 Suited to employment in American brand moving back East (6) | |
| L | US (american) + label(brand) moving e = USABLE |
| 39 Good character made Ray evergreen (6) | |
| I | g(good) + air (character) + (ray)* = GARRYA |
| 40 Increased endless uncertainty in elder drunk (7) | |
| (elder)* around doubt – t (uncertainty) = REDOUBLED | |
| 41 Not, on reflection, certain Dad’s last to be bald (6) | |
| Rev. not + sure (certain) + d (Dad’s last) = TONSURED | |
| Down | |
| 1 Excluding the fifth, 19 special hundreds (6) | |
| Cantered (19) – e + s (special_ = CANTREDS | |
| 2 Church area guide welcoming Catholic (7) | |
| N | channel (guide) around c (catholic) = CHANCEL |
| 3 Nice children from Dresden snubbed (4) | |
| E | Kinder (children from Dresden) – r = KIND |
| 4 Heart of violet fades, it’s been out for ages (5) | |
| S | ol (heart of violet) + dies (fades) = OLDIE |
| 5 Scottish disprove guard dressed in ruff (6) | |
| ree(ruff) around (argue)* = REDARGUE | |
| 6 Sword held by finest of cavaliers (5) | |
| F | Hidden finEST OF Cavaliers = ESTOC |
| 7 Primarily some climbing along ladders and invading during onslaught (7) | |
| I | starts of letters in clue = SCALADO |
| 8 Ice-cream sale item a member rejected (6) | |
| L | Rev. lot (sale item) + a + leg (member) = GELATO |
| 9 Modern philosopher‘s tone worried head off clergyman (8) | |
| L | (tone)* + cleric (clergyman) – c = NEOTERIC |
| 10 Mocked up the German spaces around base (5) | |
| Rev. der (the German) + ens (spaces) around e (base) = SNEERED | |
| 17 Bones chap’s taken from amulet (4) | |
| S | talisman (amulet) – man (chap) = TALI |
| 18 Briefly anxious, missing grand wife in Bonn (4) | |
| H | fraught (anxious) – t – g (grand) = FRAU |
| 20 Skilled musician‘s overcautious playing, missing cue perhaps (8) | |
| A | (overcautious – cue)* = VIRTUOSO |
| 22 A plan to get husband for Chinese nurse (4) | |
| P | a + map(plan) + h (husband) = AMAH |
| 23 Eggs put into hollow ceramic reptile (4) | |
| E | roe(eggs) in cc (hollow ceramic) = CROC |
| 24 Game that is enthralling cricket club bouncer possibly (7) | |
| C | ie (that is) around cc (cricket club) + ball (bouncer possibly) = ICEBALL |
| 25 Aussie conmen forged errors to collect foremost lost art (7) | |
| R | (errors)* around art – a (foremost lost) = RORTERS |
| 27 Boat pound on river in the Fens (6) | |
| E | beat (pound) + eau (river in teh Fens) = BATEAU |
| 28 It forms a complex DNA Gail’s written up (6) | |
| A | (DNA gail)* = LIGAND |
| 29 Beloved stopped receiving Listener (6) | |
| ended (stopped) around ear(listener) = ENDEARED | |
| 30 Thoroughly searched and found college further north (5) | |
| sourced (found) moving c (college) north = SCOURED | |
| 31 Nettle’s relative right about match (5) | |
| T | r(right) + a (about) + meet (match) = RAMEE |
| 32 Maybe Queens both spending time regularly below chocolate tree (5) | |
| E | cat(queen) x 2 – t + bElOw = CACAO |
| 36 Communist turned up in fine new plant (4) | |
| D | rev. red (communist) in df (fine) + n (new) = FERN |

I’m glad you enjoyed my puzzle Twencelas and thank for your blog. Much appreciated.
I didn’t get to solve the puzzle but reading through the blog has given me ample idea of what a beautifully set puzzle it is.
The blog is quite detailed and excellently written. Learnt a lot from it.
CUCKOO and CACAO were my top faves.
Thanks, Vismut and twencelas!
What a wonderfully-crafted (!) puzzle – fun to do and rewarding to solve.
Twencelas, thanks for the comprehensive blog… that too was well-crafted.
Yes very enjoyable, even though the final house does not bear much resemblance to the real one! But a fun puzzle and a great topic to get to know more.
Loved 100,000 nuts!
Loved this puzzle and learned something as always from Vismut. Many thanks to her and twencelas.