Small-minded about Romeo charming (6)
I believe the answer is:
pretty
'charming' is the definition.
(thesaurus)
'small-minded about romeo' is the wordplay.
'small-minded' becomes 'petty' (synonyms).
'about' means one lot of letters goes inside another.
'romeo' becomes 'r' (phonetic alphabet: alpha, bravo, charlie etc.).
'petty' going around 'r' is 'PRETTY'.
(Other definitions for pretty that I've seen before include "pulchritudinous" , "Rather attractive" , "Fairly - good-looking" , "Delicately attractive" , "Attractive in delicate way" .)