Italian city mainly industrial, like another Naples originally (5)
I believe the answer is:
milan
'italian city' is the definition.
(I've seen this before)
'mainly industrial like another naples originally' is the wordplay.
'originally' indicates taking the first letters.
The initial letters of 'mainly industrial like another naples' is 'MILAN'.
(Other definitions for milan that I've seen before include "European city" , "City of northern Italy" , "Italian city with La Scala opera house" , "Capital of Lombardy" , "province" .)