The unclued lights are of a specific kind. Additionally each is a legitimate inflected headword in Chambers. Elsewhere, ignore one acute accent and an apostrophe.
 

Across

 
4    By the way, black weapon is a valuable curio (9, two words)
9    C.O.O.L.E.R. characters in the mail? (10, two words)
12    Types of lenses — 1000 nice ones distributed (7)
14    Undertaking in 1A is cut by Harpagon (5)
16    Difficulty with butlers at heart will annoy (6)
21    Puss goes to and through such a passage (8)
22    Means to an end suggests food and games (7)
24    Reduced money for lounge (4)
25    Equipment engineer’s opening for bird (4)
27    Ballerina talked of Parisian water feature (7)
28    Early drink for beautiful fairy in a fit, squiffy (8)
33    US head will improvise making pasta (6)
34    New suite-cases! (5)
37    Participated in a demo and fought back (7)
39    Sign of threatening weather troubled Mold’s court (10, two words)
40    Linguistic scholar and newspaperman repeated obstinately (9)
41 + 103 is far too much! (5)
 

Down

 
1    Craftsmen repaired seat-back with miner (13, two words)
2    During the morning, practised or entertained (6)
3    Information about knock out for military plane (6)
4    Isolde edited monthly magazines (6)
6    Durable cross disappears from outside (7)
7    Dirtiness oddly reveals prohibitionists (5)
8    Scientific study of tulip’s head in alpine garden (8)
10    Titled ladies sent roughly half a dozen Liverpudlians outside (13)
13    Jack – he keeps at it (7)
15    British Academy deceives Shakespearian rustics (6)
17    Attack women leaving drinking bout (6)
19    Mendicant dervishes showing no sign of hesitation at the start of each
month (7)
20    Conurbations having connections with Ivory Coast (6)
23    Cut off in the middle of grounds at art gallery (8)
26    Metalworkers from Chester (7)
29    Numerous books in awfully loud covers (6)
30    Distinction working in time (6)
31    Mudflats in the Kendal area, apparently (6)
36    Dainty put on hold – not starting (4)
 
A first prize of £30 for the first correct solution opened on 29 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 2179, The Spectator, 22 Old Queen Street, London SW1H 9HP. Please allow six weeks for prize delivery.