Joy's crushed by Romeo having intercourse (9)
I believe the answer is:
relations
'intercourse' is the definition.
(I know that intercourse can be written as relations)
'joy's crushed by romeo' is the wordplay.
'joy's' becomes 'elation's' (elation is a kind of joy).
'crushed by' means one lot of letters go next to another (in a down clue, some letters go on top of others).
'romeo' becomes 'r' (phonetic alphabet: alpha, bravo, charlie etc.).
'elations' put after 'r' is 'RELATIONS'.
'having' acts as a link.
(Other definitions for relations that I've seen before include "granny and grandad, perhaps?" , "Family members" , "kinsfolk" , "liaison" , "They're connected by blood or marriage" .)