Boy with yen for peeress (4)
I believe the answer is:
lady
'peeress' is the definition.
('lady' can be a synonym of 'peeress')
'boy with yen' is the wordplay.
'boy' becomes 'lad' (lad is a kind of boy**).
'with' is a charade indicator (letters next to each other).
'yen' becomes 'y'.
'lad'+'y'='LADY'
'for' is the link.
(Other definitions for lady that I've seen before include "High-class woman" , "Noble" , "See 19" , "Female title" , "Woman, maybe titled" .)