One not going out after retirement (9)
I believe the answer is:
insomniac
'going out after retirement' is the definition.
Both the answer and definition are adjectives. Maybe they are linked in a way I don't understand?
'one not' is the wordplay.
I cannot really see how this works, but
'one' could be 'i' (Roman numeral) and 'i' is located in the answer.
'not' could be 'o' (I've seen this in other clues) and 'o' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for insomniac that I've seen before include "One lying awake" , "Can't drop off" , "This person can't sleep" , "Person finding it difficult to sleep" , "Habitually sleepless person" .)