The French leading fit group (6)
I believe the answer is:
league
'group' is the definition.
The answer is an example.
'the french leading fit' is the wordplay.
'the french' becomes 'le'.
'leading' says to put letters next to each other.
'fit' becomes 'ague' (I've seen this before).
'le'+'ague'='LEAGUE'
(Other definitions for league that I've seen before include "class" , "Group of teams competing over a period" , "some mileage?" , "Association - old measure of distance" , "distance at sea" .)