Doc is the compiler of this Spectator crossword.
The preamble to the puzzle reads as follows:
The unclued lights can be arranged to grow from 3 to 11 letters in length, each being an anagram of its predecessor and an extra letter.
Apart from a couple of obscure references (at least to me), including nattier blue and Polari, this was mainly a straightforward and enjoyable solve. It was just difficult enough to be satisfying to solve. The string of words from 3 to 11 letters (highlighted in the grid below, starting with EAT and ending with INCINERATES) wasn’t difficult to work out although I had to check that NECTARIES was a word.
Thanks, Doc.

| ACROSS | ||
| 1 | INCINERATES | 
 (11) 
 | 
| 7 | BAT | 
 Equipment for Bell, Athey and Trescothick initially (3) 
 | 
| B(ell) A(they) T(rescothick) [initially]Ian Bell, Bill Athey and Marcus Trescothick were all English batsmen. | ||
| 11 | RECANT | 
 (6) 
 | 
| 13 | MENACES | 
 Male folk star’s alarming words (7) 
 | 
| MEN (“male folk”) + ACES (“stars”) | ||
| 15 | BRIAR | 
 Pipe valley running through Britain (5) 
 | 
| RIA (“valley”) running through Br. (Britain) | ||
| 16 | STAID | 
 Reportedly remained stolid (5) 
 | 
| Homophone/pun/aural wordplay [reportedly] of STAYED (“remained”) | ||
| 17 | MESIAL | 
 Middle of emails edited (6) 
 | 
| *(emails) [anag:edited] | ||
| 18 | BIDET | 
 Nameless President has time on the loo (5) 
 | 
| (Joe) BIDE(N) lacking an N [nameless] has T (time) | ||
| 20 | CRANIA | 
 Brainboxes managed to infiltrate spy agency (6) 
 | 
| RAN (“managed”) to infiltrate CIA (Central Intelligence Agency, so “spy agency”) | ||
| 21 | PETER | 
 Thorpe, terrified somewhat of safe-cracker (5) 
 | 
| PETER (“safe”) cracking into “thorPE TERrified” [somewhat] | ||
| 22 | REELING | 
 Doddery, maybe, when dancing in Aviemore? (7) 
 | 
| Double definition | ||
| 27 | CERTAIN | 
 (7) 
 | 
| 29 | ARRAS | 
 Hanging back in disarray (5) 
 | 
| Hidden [back in] “diSARRAy” | ||
| 30 | ELAPSE | 
 English earl touring alps negotiated pass (6) 
 | 
| E (English) + E (earl) touring *(alps) [anag:negotiated] | ||
| 32 | AORTA | 
 Blood carrier, a kind heading off on ambulance initially (5) 
 | 
| A + (s)ORT (“kind” with its heading off) on A(mbulance) [initially] | ||
| 34 | POLARI | 
 The North Star gets cut in form of cant or slang (6) 
 | 
| POLARI(s) (“The North Star”, gets cut)Polari is a form of slang used in some British subculutures and professions. | ||
| 36 | ULCER | 
 Blemish beautiful cereals boxes (5) 
 | 
| Hidden in [boxes] “beautifUL CEReals” | ||
| 37 | CATER | 
 (5) 
 | 
| 38 | RWANDAN | 
 African who gets the stick, having rushed around (7) 
 | 
| WAND (“stick”) having RAN (“rushed”) around | ||
| 39 | REGION | 
 Area occupied by some flustered foreigners (6) 
 | 
| REGION is an anagram [flustered] of several contiguous letters of (f)OREIGN(ers) | ||
| 40 | EAT | 
 (3) 
 | 
| 41 | SUSAN GEORGE | 
 She played Amy for Sam in 1971 with Sarandon and Clooney (5,6) 
 | 
| SUSAN (Sarandon) and GEORGE (Clooney)The actress Susan George played a character called Amy in the 1970 thriller Straw Dogs, directed by Sam Peckinpah. | ||
| DOWN | ||
| 1 | IN MEMORIAM | 
 Collapsed mine with folly marks final tribute (2,8) 
 | 
| *(mine) [anag:collapsed] with MORIA (“folly”) + M (marks) | ||
| 2 | CANISTER | 
 (8) 
 | 
| 3 | NECTARIES | 
 (9) 
 | 
| 4 | RESTING PLACE | 
 Tracing sleep maybe, and where to find it? (7,5) 
 | 
| *(tracing sleep) [anag:maybe] | ||
| 5 | TALIBAN | 
 Fundamentalist army replace subhuman’s head with time (7) 
 | 
| Replace the head of CALIBAN (a subhuman in character in Shakespeare’s The Tempest) with T (time) to get T(ALIBAN) | ||
| 6 | STRIDENT | 
 Second passenger aircraft making a lot of noise (8) 
 | 
| S (second) + TRIDENT (“passenger airport”) | ||
| 7 | BRIBE | 
 Born to make fun of drug incentive (5) 
 | 
| B (born) + RIB (“to make fun of”) + E (ecstasy, so “drug”) | ||
| 8 | TARE | 
 (4) 
 | 
| 9 | LEXEME | 
 Latin law primarily explaining Middle Eastern linguistic unit (6) 
 | 
| LEX (“Latin” for “law”) + [primarily] E(xplaining) M(Iddle) E(astern) | ||
| 10 | BASIC | 
 Elementary book academy faithfully reproduced (5) 
 | 
| B (book) + A (academy) + SIC (“faithfully reproduced”) | ||
| 12 | NATTER | 
 Chinwag with Blue. I left (6) 
 | 
| I left NATT(i)ER (a shade of “blue”) | ||
| 14 | DAVID CAMERON | 
 Random advice doled out for PM (5,7) 
 | 
| *(random advice) [anag:doled out] | ||
| 19 | TRANSIENCE | 
 (10) 
 | 
| 21 | PARSONAGE | 
 Priest’s crime taking time in clerical residence (9) 
 | 
| P (priest) + ARSON (“crime”) taking AGE (“time”) | ||
| 23 | LEARNERS | 
 Fifty folk with a wage are beginners (8) 
 | 
| L (50, in Roman numerals) + EARNERS (“folk with a wage”) | ||
| 24 | MARAUDER | 
 Pirate state with a Durer composition (8) 
 | 
| MA (Massachuetts, so “state”) with *(a durer) [anag:composition] | ||
| 25 | FRACAS | 
 Amateur in neckwear raised uproar (6) 
 | 
| A (amateur) in <=SCARF (“neckwear”, raised) | ||
| 26 | SEA LEGS | 
 The Navy’s firmest supporters (3,4) 
 | 
| Cryptic definition | ||
| 28 | INROAD | 
 Attack the entranceway? (6) 
 | 
| IN (“entrance”) + ROAD (“way”) | ||
| 31 | ELAND | 
 Animal making dash, getting trapped ultimately (5) 
 | 
| ELAN (“dash”) getting (trappe)D [ultimately] | ||
| 33 | OCTET | 
 Musicians content to leave Egypt after 31 days (5) 
 | 
| [content to leave] O(cte)T after Oct. (October, so “31 days”) | ||
| 35 | OCHE | 
 Pinochet drops pint here? (4) 
 | 
| (pin)OCHE(t) drops PINTThe oche is the line from which a darts player throws their darts. | ||
Small typo in the puzzle number, it should be 2,724.
I wondered about TERA- as an option for 8d but as Chambers shows it only as a prefix I also went with TARE.
For those new to the Spectator, you may not know that Doc is also the Crossword Editor and is perhaps better known to Guardian solvers here as Maskarade.
This article by Doc on 50 Yeras of the Spectator Crossword may be of interest.
Thanks to loonapick and Doc.
Jay @1 Not picking holes – honestly.
I just find it ironic that you wrote “Yeras” instead of “Years”.
Looks like you need to be a subscriber to read it 😞
Puzzle title fixed
Or, you could look here: https://web.archive.org/web/20220427051207/https://www.spectator.co.uk/article/fifty-years-of-the-spectator-crossword