Retires to Italian city overlooking the outskirts of Naples (5,2)
I believe the answer is:
turns in
'retires' is the definition.
('turn in' can be a synonym of 'retire')
'italian city overlooking the outskirts of naples' is the wordplay.
'italian city' becomes 'turin' (I've seen this in another clue).
'overlooking' indicates putting letters inside (in a down clue, some letters go above others).
'the outskirts of' says to hollow out the word (remove centre letters) (letters on the edges or outskirts are used).
'naples' with its middle taken out is 'ns'.
'turin' going around 'ns' is 'TURNS-IN'.
'to' is the link.
(Other definitions for turns in that I've seen before include "Voluntarily hands over" , "Retires" , "goes to bed" , "Goes home" .)