Ecstasy in heart perhaps before love leaves (7)
I believe the answer is:
oregano
'leaves' is the definition.
(I've seen this before)
'ecstasy in heart perhaps before love' is the wordplay.
'ecstasy' becomes 'e' (informal term for the drug).
'in' is an insertion indicator.
'heart perhaps' becomes 'organ' (heart is a kind of organ).
'before' is a charade indicator (letters next to each other).
'love' becomes 'o' (In tennis, 'love' means 'zero').
'e' put within 'organ' is 'oregan'.
'oregan'+'o'='OREGANO'
(Other definitions for oregano that I've seen before include "Kitchen herb" , "food flavouring" , "Mediterranean herb" , "Aromatic culinary herb" , "Pizza herb" .)