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?' suggests removing the centre (I've seen 'losing 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" .)