I don't like that Romeo — he's rude (4)
I believe the answer is:
boor
'he's rude' is the definition.
(term for a person with no manners)
'i don't like that romeo' is the wordplay.
'i don't like that' becomes 'boo'.
'romeo' becomes 'r' (phonetic alphabet: alpha, bravo, charlie etc.).
'boo'+'r'='BOOR'
(Other definitions for boor that I've seen before include "Rude, uncultured type" , "Rude, uncultivated person" , "Lout" , "oaf" , "oik" .)