Six unclued lights are the names of traditional English county towns with one letter misprinted so as to form new words. The correct letters could give 26, examples of which are 1A, 17 and 22A.

Across

7 Sound of kitten in hiding-place (3)

11 Mechanical playwright heard E strings (6)

13 Aberdonian angler with chatter about fish (7, hyphened)

15 Short course is wanting (5)

16 Ruby gutted a grouse (5)

18 River one’s learning about (5)

23 Parrot flying round English magistrate (7)

30 Slack student (no saint) began to play (5)

31 Left out...