Possible Clues:

• Like a piece by Chopin? Criticise loudly - missing an A natural is wrong
• Curl Anton developed during the night
• In no state to become active in the dark hours?
• Is Conal about to turn in the dark?
• Sounds as if it's for the knight to get no hundred back with a fifty
• Untouchable regularly seen about to go off, shunning the light
• In no state to change working at night
• Clan to run off at night
• Call it a night mid-evening, with Lorna out of sorts over club joining trade union
• As eg badgers do around corner, at least initially