The unclued lights and eight clued without thematic definition are of a kind, expressly confirmed in a section of Chambers.

Across

4 Artisan on board, apparently (9)

9 Airline having to secure shopping accessory (10, two words)

11 Alton United seen regularly (5)

12 State loudly and close the innings (7)

14 It’s terrible about half of the lake having dried up (5)

15 Maintain he has left Michael in trouble (5)

16 Washes electronic instruments (6)

21 Waterproofs for artist in river up north (8)

22 Weeks at school in one or more stations (7)

24 Caesar’s for...