Unveiled, she lent beauty to mythology (5)
I believe the answer is:
helen
'beauty to mythology' is the definition.
(beautiful woman in Greek myth)
'unveiled she lent' is the wordplay.
'unveiled' indicates a hidden word (the answer can be unveiled from inside the clue).
'HELEN' can be found hidden inside 'she lent'.
(Other definitions for helen that I've seen before include "Spartan beauty" , "Woman abducted to Troy" , "Was this the face that launch'd a thousand ships?" , "Girl" , "Trojan war beauty" .)