Legendary siren (7)
I believe the answer is:
lorelei
'legendary siren' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for lorelei that I've seen before include "Dangerous female" , "enchantress" , "Rhine rock of siren legend" , "Rhine Rock where siren lived" , "Great Rock on the Rhine where sirens lived in legend" .)