Unclued lights can be grouped into three triplets, each associated in a different sense with a keyword to be discovered, of which the title suggests a topical example

Across

7 Assembly line described by writer I don’t know (6)

12 Smaller flower is rarity, but gets propagated (9)

13 Dido laughed, admitting mistaken views (5)

15 Magic as hospital overcomes shortage (9, two words)

16 Buttress, stone, penetrated by Edmund (6)

20 Celebrate about weed doing farrier’s work (7)

21 Do a Chinese for Mormon perhaps (6)

24 Loose women once simpered stupidly (8)

26 One terrible noise echoing...