What makes Salerno a famous city (3,7)
I believe the answer is:
new orleans
'a famous city' is the definition.
'what makes salerno' is the wordplay.
'what' becomes 'new' (I am not sure about this - if you are sure you should believe this answer much more).
'makes' indicates an anagram.
'salerno' anagrammed gives 'orleans'.
'new'+'orleans'='NEW ORLEANS'
(Other definitions for new orleans that I've seen before include "US city" , "City of Louisiana" , "Devastated city" , "port city in the south" .)