Young woman in glasses (4)
I believe the answer is:
lass
'young woman' is the definition.
(informal term for a young woman)
'in glasses' is the wordplay.
'in' indicates the answer is hidden within the clue.
'LASS' can be found hidden inside 'glasses'.
(Other definitions for lass that I've seen before include "Girl (of Richmond Hill?)" , "Sweet resident of Richmond Hill?" , "Young woman, girl" , "Scottish girl" , "Familiar form of address for female" .)