The dejection of the French couple (7)
I believe the answer is:
despair
'the dejection' is the definition.
(thesaurus)
'of the french couple' is the wordplay.
'of the french' becomes 'des' ('of the' in French).
'couple' becomes 'pair' (synonyms).
'des'+'pair'='DESPAIR'
(Other definitions for despair that I've seen before include "displaying lack of optimism" , "Complete absence of hope" , "Hopeless" , "State of having lost all hope" , "Lose heart" .)