Condition preventing one being out after dark? (8)
I believe the answer is:
insomnia
'dark?' is the definition.
The definition and answer can be both states of affairs as well as being singular nouns.
Perhaps there's an association between them I don't understand?
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for insomnia that I've seen before include "Not getting off" , "Inability to drop off" , "Habitual inability to sleep (8)" , "Habitual sleeplessness" , "State of chronic sleeplessness" .)