The French fellows in court showing mercy (7)
I believe the answer is:
clement
'mercy' is the definition.
(I've seen this before)
'the french fellows in court' is the wordplay.
'the french' becomes 'le'.
'fellows' becomes 'men' (I've seen this before).
'in' means one lot of letters goes inside another.
'court' becomes 'ct'.
'le'+'men'='lemen'
'lemen' inserted inside 'ct' is 'CLEMENT'.
'showing' is the link.
(Other definitions for clement that I've seen before include "nice" , "Pope once" , "- - Attlee (PM)" , "chap" , "opponent for Winston" .)