The French fever in a group of clubs (6)
I believe the answer is:
league
'a group of clubs' is the definition.
(eg the Premier League)
'the french fever' is the wordplay.
'the french' becomes 'le' ('the' in French).
'fever' becomes 'ague' (I've seen this before).
'le'+'ague'='LEAGUE'
'in' is the link.
(Other definitions for league that I've seen before include "Old distance measure of about three miles" , "some mileage?" , "Former measure of distance, usually about three miles" , "Federation" , "Old units of distance" .)