Freak hollow swallows street in Naples (7)
I believe the answer is:
deviant
'freak' is the definition.
(thesaurus)
'hollow swallows street in naples' is the wordplay.
'hollow' becomes 'dent' (both can mean an impression or indentation).
'swallows' indicates putting letters inside.
'street in naples' becomes 'via' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'dent' enclosing 'via' is 'DEVIANT'.
Can you help me to learn more?
(Other definitions for deviant that I've seen before include "Irregular" , "(One) behaving differently from accepted standards" , "not behaving properly?" , "Departing from accepted standards" , "Abnormal" .)