Young woman in glasses (4)
I believe the answer is:
Here is my best explanation:
'young woman' is the definition.
(lass is a kind of young woman)
'in glasses' is the subsidiary indication.
'in' indicates a hidden word.
'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 (-. Eng.)", "A girl", "Young woman, girl", "Damsel", "Girl, young woman" and "Scottish girl".)