41, 1A, 10 (seven words in total) is a description of a phenomenon. Remaining unclued lights, including one of two words and three of three words, either singly, paired or as a trio, form four examples of this phenomenon. All are confirmed in the ODQ (8th ed.)

Across

11 Leaf parts of liana ice destroyed (8)
12 Agreed drug hidden in grass must return (4)
13 Fish, internally cold and blue (4)
14 Split lip — scare for breathing orifice (8)
16 African statesman’s vengeance on criminals (6)
18 It’s complete in French flag (6)
20 With hi-hat, Mary’s beaten uneven beat (9)
21 In trouble, on digging into posh spread (7, three words)
22 After dessert, king’s in plane (6)
23 Seemingly good and bad, mostly like Esau? (6)
26 Dye a German put on reptile (7)
29 Sing that drunkenly around grand party (9, two words)
31 Poet, a fellow dissecting rodent (6)
32 Skilled poet did this? (6)
37 Latest art nouveau, art failing (8)
39 Person joining bank? (4)
40 Plant providing beer, neat in a cocktail (8, two words)

Down

2 Fur smuggled without expression of surprise (6)
3 Film about a cut off bridge (7)
4 Ruling person who summons provocateur (7)
5 See gagster’s funny treats for kids (10, two words)
6 Old poem about ruler (4)
7 Hastened through German or Italian town (7)
8 Play area imp and boy went to the top of again (9)
9 Gold in a state that is showing some heat (7)
13 Polish jewel endlessly (3)
17 Elegant hotel compound in English city (10)
19 Gassed, in state having lost colour externally (9)
25 Lack of belief in aunt, if changing husband (7)
27 General began to protect navy (7, hyphened)
28 Like the heart of my sweetheart (7)
30 Thessalian king suffering, even heartless (6)
35 Advice to study, we’re told (4)
36 A number of Germans were dishonest (4)

A first prize of £30 for the first correct solution opened on 9 March. 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 2445, The Spectator, 22 Old Queen Street, London SW1H 9HP. Please allow six weeks for prize delivery./>