Romeo's after a woman, always (4)
I believe the answer is:
ever
'always' is the definition.
(synonyms)
'romeo's after a woman' is the wordplay.
'romeo' becomes 'r' (phonetic alphabet: alpha, bravo, charlie etc.).
'after' says to put letters next to each other.
'a woman' becomes 'eve' (Eve is an example).
'r' put after 'eve' is 'EVER'.
(Other definitions for ever that I've seen before include "In perpetuity" , "Eternity" , "To the end of time" , "Always and permanent" , "Perpetually" .)