Softens, finding the French trapped in leases (7)
I believe the answer is:
relents
'softens' is the definition.
('relent' can be a synonym of 'soften')
'the french trapped in leases' is the wordplay.
'the french' becomes 'le'.
'trapped in' is an insertion indicator.
'leases' becomes 'rents' ('rent' can be a synonym of 'lease').
'le' inserted within 'rents' is 'RELENTS'.
'finding' is the link.
(Other definitions for relents that I've seen before include "is slackening" , "Comes round" , "Shows mercy" , "Eases off" , "Becomes less severe and more lenient" .)