Is she likely to lose heart? (4)
I believe the answer is:
lily
'is she' is the definition.
'likely to lose heart?' is the wordplay.
'to lose heart?' says to hollow out the word (remove centre letters) (I've seen 'to lose heart' mean this).
'likely' with its centre removed is 'LILY'.
(Other definitions for lily that I've seen before include "Flower; girl's name" , "Plant like an amaryllis" , "White" , "Trumpet-shaped flowering plant" , "Plant with showy pendulous flowers" .)