Hopelessness of French couple following son (7)
I believe the answer is:
despair
'hopelessness' is the definition.
(despair is a kind of hopelessness)
'of french couple following son' is the wordplay.
'of french' becomes 'de'.
'couple' becomes 'pair' ('pair' can be a synonym of 'couple').
'following' says to put letters next to each other.
'son' becomes 's'.
'pair' after 's' is 'spair'.
'de'+'spair'='DESPAIR'
(Other definitions for despair that I've seen before include "Despond" , "Lose or lack hope" , "Lose heart" , "Misery" , "Be without hope" .)