Of Troy (6)
(Other definitions for helen that I've seen before include "Legendary beauty of Troy" , "Ship launcher" , "Trojan war beauty" , "Woman who launched a thousand ships?" , "Famous classical beauty" .)
'of troy' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for trojan that I've seen before include "Horse filled with Greek soldiers" , "Subject of King Priam" , "This legendary horse was wooden and hollow" , "Paris for one" , "Of Troy or its people" .)