The woman in the lens (5)
I believe the answer is:
helen
'the woman' is the definition.
'in the lens' is the wordplay.
'in' indicates a hidden word.
'HELEN' is hidden in the letters of 'the lens'.
(Other definitions for helen that I've seen before include ""The face the launched 1,000 ships"" , "Famous beauty of Troy" , "the Parisian woman?" , "The Greek army sailed to Troy to get her back" , "Woman who launched a thousand ships?" .)