Girl probably disheartened (4)
I believe the answer is:
lily
'girl' is the definition.
(I've seen this before)
'probably disheartened' is the wordplay.
'probably' becomes 'likely' ('likely' can be a synonym of 'probably').
'disheartened' means to remove the middle letters.
'likely' with its middle removed is 'LILY'.
(Other definitions for lily that I've seen before include "Bulbous plant with trumpet-shaped flowers" , "Flower much associated with funerals" , "Easter flower" , "Plant with showy pendulous flowers" , "Flower, maybe of the valley" .)