City and Italian city-dweller about to appear in US city? Magic (10)
I believe the answer is:
necromancy
'magic' is the definition.
(I've seen this before)
'city and italian city-dweller about to appear in' is the wordplay.
'city' becomes 'ec' (the City of London postcode).
'and' becomes 'n' (common abbreviation for 'and').
'italian city-dweller' becomes 'roman'.
'about' means one lot of letters goes inside another.
'to appear in' becomes 'cy' (I can't justify this - if you can you should believe this answer much more).
'n'+'roman'='nroman'
'ec' inserted into 'nroman' is 'necroman'.
'necroman'+'cy'='NECROMANCY'
'us city?' acts as a link.
This may not be correct. Some or all of it may belong to another bit of the clue.
(Another definition for necromancy that I've seen is " magic".)