Mature woman, her youth sadly finished (4)
I believe the answer is:
lady
'mature woman' is the definition.
(I've seen this before)
'her youth sadly finished' is the wordplay.
I cannot quite understand how this works, but
'youth' could be 'lad' (I've seen this before) and 'lad' is located in the answer.
A single letter 'y' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for lady that I've seen before include "Title for a knight's wife" , "Noble" , "Lord's wife - peeress's title" , "Luck, for example" , "See 19" .)