A young lady in glasses (4)
I believe the answer is:
lass
'a young lady' is the definition.
(I know that lass is a type of young lady)
'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 "Damsel" , "Scottish girl" , "Young woman (-. Eng.)" , "Young woman, girl" , "Miss" .)