Helen of Troy's mother (4)
I believe the answer is:
leda
'helen of troy's mother' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for leda that I've seen before include "One ravished" , "- - and the Swan (mythology)" , "She was seduced by Zeus disguised as a swan" , "small satellite of Jupiter" , "Mother of Helen and Pollux" .)