Romeo, a Parisian character (4)
I believe the answer is:
rune
'character' is the definition.
(I know that rune is a type of character)
'romeo a parisian' is the wordplay.
'romeo' becomes 'r' (phonetic alphabet: alpha, bravo, charlie etc.).
'a parisian' becomes 'une' ('a' in French).
'r'+'une'='RUNE'
(Other definitions for rune that I've seen before include "Ancient character" , "Old alphabet letter" , "Letter of an ancient Germanic alphabet" , "Early symbol used in carvings" , "Mystic symbol" .)