Autograph on alternative Italian guy (6)
I believe the answer is:
signor
'italian guy' is the definition.
(Italian title for a man)
'autograph on alternative' is the wordplay.
'autograph' becomes 'sign' (I've seen this before).
'on' is a charade indicator (letters next to each other).
'alternative' becomes 'or'.
'sign'+'or'='SIGNOR'
(Other definitions for signor that I've seen before include "Title of Italian-speaking man" , "Title of Italian man" , "Italian gentleman" , "Italian mister" , "Guy in Rome" .)