A grim end to our love (5)
I believe the answer is:
amour
'love' is the definition.
('love' in French)
'a grim end to our' is the wordplay.
'end' indicates one should take the final letters.
The last letter of 'grim' is 'm'.
'a'+'m'+'our'='AMOUR'
(Other definitions for amour that I've seen before include "(Secret) lover" , "beloved" , "Secretive affair" , "Romantic liaison" , "illicit liaison" .)