Tragic girl mixed claret with ecstasy (7)
I believe the answer is:
electra
'tragic girl' is the definition.
(heroine of ancient Greek tragedy)
'mixed claret with ecstasy' is the wordplay.
'mixed' is an anagram indicator.
'with' is an insertion indicator.
'ecstasy' becomes 'E' (informal term for the drug).
'claret' is an anagram of 'elctra'.
'elctra' enclosing 'e' is 'ELECTRA'.
(Other definitions for electra that I've seen before include "Mythical woman with a complex?" , "heroine of Greece" , "vengeful daughter" , "Complex girl" , "Greek mythic woman has an odd Celt ear" .)