Irish leader disposed of drug for operatic heroine (6)
I believe the answer is:
isolde
'operatic heroine' is the definition.
(I've seen this before)
'irish leader disposed of drug' is the wordplay.
'leader' indicates taking the first letters.
'disposed of' becomes 'sold' (I've seen this before).
'drug' becomes 'e' (e is another name for ecstasy).
The initial letter of 'irish' is 'i'.
'i'+'sold'+'e'='ISOLDE'
'for' is the link.
(Other definitions for isolde that I've seen before include "heroine (sic)" , "Tristan's beloved" , "for Tristram" , "Legendary lover" , "princess of legend" .)