The unclued lights (one of two words), individually or as two pairs, are of a kind. Elsewhere, ignore one accent.
 

Across

1           Groups of helpers providing accompaniments to pop-singers (8)
5           Trembling like fish (6)
14         Some weekend supplement (3)
16         Lionel wrecked ornamental metalwork (6)
17         Pack animal in a shopping plaza from the east (5)
18         Climber following others’ lead, like a sheep (5)
20         Early satellite rattles around (7)
22         Minerva regularly gripped by desire to win (7)
24         Scandalous episode of trade show in unopened eatery (7)
25         Clans parking in groups (5)
26         Toss last bit of pepper into casserole (5)
28         Flies second in six going west (7)
31         Lyre from shelter made from 6 (7)
33         Set aside half of area in the shape of a ring (7)
37         Gave one’s playmates a hand? (5)
38         Character from Highland festival around mid-July (5)
40         Unusual version of Love divine (3)
42         Old flier’s info about stunning blow (6)
 

Down

1           It enables operators to link words as one bachelor is troubled (13, two words)
2           Cordelia’s opening her father’s net (5)
3           Group in Arctic eagerly reveals cold period (6, two words)
6           Protects US actress (7)
7           Distributes onions Mum dropped (6)
10         Stand about, just to rile constituents (6)
11         Small county ordered these linen items (9)
12         Suitable reporter (13)
15         Compound answer covering empty argument (7)
19         This attendant involved with chartered surveyor could be disgraceful (9)
23         Big thaw causes river to swamp shelter (7)
27         Perennial weed singularly sown by dissipate youths? (7, two words)
30         Could be a gricer, a knight or a king (6)
32         Pastry seen at first in Polynesian island group (6)
34         Shade in France — endlessly dull and cloudy (5)
35         Law active in part of Palestine (5)
36         Meat and egg pie, butter, without a touch of mustard (4)

 
A first prize of £30 for the first correct solution opened on 21 October. 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 2428, The Spectator, 22 Old Queen Street, London SW1H 9HP. Please allow six weeks for prize delivery.