The unclued lights are connected by 33/23. One pair of unclued lights gives one context, in which two further pairs of unclued lights are followers of 33/23; remaining unclued lights, in another sense, are 33/23’s predecessors.
 

Across

1    Nasty offer about shock treatment for responsive organ (8)
8    Rubber — a lump’s returned (4)
11    Rarer Islamic itinerant message-bringers (12, hyphened)
12    It leaves soldiers with white marks (5)
14    Final, long ending shows addition to bill (7)
16    Greek maiden’s torment on earth (5)
17    Eddy in Glasgow is to go left (4)
22    Artist’s manipulated a ruler (8)
24    Chaos in bit of spring border (6)
25    Scot’s moment, tense, to break safe (6)
27    Millions judge youngster (7)
29    One in bed with jester — queen? (8, hyphened)
34    Capital city gets great fort back (4)
35    Tall gull has regularly withdrawn wing (5)
37    Clergyman, did you say? Come again (7)
38    Sailor endlessly boring Arab boy (5)
39    Green teapot I ordered, needing to settle in advance (12)
40    Reality of county deprived of vote (4)
41    Extremely shady yard in which old lady cut the flowers fusing together (8)
 

Down

1    Poet’s thrill as Gemma loves to strip off (6)
3    Evoke what’s allowed on-line? (6)
4    At sea on yacht, one’s faster than light (7)
5    Finds way around bright corn, it’s said (10)
7    Operator gives greater help in difficulty (11)
9    Raising drink, Irish journo provides source of oil (9, two words)
13    Craft of snake in pine tree’s top (8)
15    Naval gun sent archers running (11, hyphened)
19    Deceptive art of excuse, a non-starter, about rising fees (10)
20    Foreign article about the bloody old king (8)
21    Sleeps uneasily, sidestepping chief rules of evidence (9)
28    E.g. rhinestone lifted great weight? (7)
32    South Africa’s fury for old African country (5)
36    No time for honesty, giving grief (4)
 
A first prize of £30 for the first correct solution opened on 22 September. There are two runners-up prizes of £20. (UK solvers can choose to receive the latest edition of the Chambers Dictionary instead of cash— ring the word ‘Dictionary’.) Entries to: Crossword 2178, The Spectator, 22 Old Queen Street, London SW1H 9HP. Please allow six weeks for prize delivery.