In love, disheartened debutante frets (6)
I believe the answer is:
erodes
'frets' is the definition.
('erode' can be a synonym of 'fret')
'in love disheartened debutante' is the wordplay.
'in' means one lot of letters goes inside another.
'love' becomes 'eros' (Greek god of love).
'disheartened' suggests removing the centre (the middle or heart is removed).
'debutante' with its centre taken out is 'de'.
'eros' going around 'de' is 'ERODES'.
(Other definitions for erodes that I've seen before include "Eats away" , "Wears away with weather" , "Wears away as by time or water" .)