One unused to early retirement? (5,3)
I believe the answer is:
night owl
'early retirement?' is the definition.
Both the definition and answer are singular nouns.
Perhaps they are linked in a way I don't understand?
'one unused to' is the wordplay.
I cannot quite see how this works, but
'one' could be 'i' (Roman numeral) and 'i' is present in the answer.
'to' is within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for night owl that I've seen before include "Person who likes to be active late in the day" , "One likes to be active late into the evening" , "Person active in the small hours" , "One working late" , "Late sleeper" .)