Embarrasses a party before elections, losing heart (7)
I believe the answer is:
abashes
'embarrasses' is the definition.
('abash' can be a synonym of 'embarrass')
'a party before elections losing heart' is the wordplay.
'party' becomes 'bash' (bash is a kind of party**).
'before' is a charade indicator (letters next to each other).
'losing heart' says to hollow out the word (remove centre letters).
'elections' with its centre taken out is 'es'.
'a'+'bash'+'es'='ABASHES'
(Other definitions for abashes that I've seen before include "Causes embarrassment" , "Embarrasses" .)