Joy telling Romeo to leave (7)
I believe the answer is:
elation
'joy' is the definition.
(I know that elation is a type of joy)
'telling romeo to leave' is the wordplay.
'telling' becomes 'relation' (to relate a story can mean to tell it).
'romeo' becomes 'r' (phonetic alphabet: alpha, bravo, charlie etc.).
'to leave' is a deletion indicator.
'relation' with 'r' taken away is 'ELATION'.
(Other definitions for elation that I've seen before include "Delight, ecstasy" , "Feeling of intense delight" , "Feeling of delight, joy" , "Feeling of joy for it alone" , "Delight, thrill" .)