The French fool in charge of brief (7)
I believe the answer is:
laconic
'brief' is the definition.
('laconic' can be a synonym of 'brief')
'the french fool in charge' is the wordplay.
'the french' becomes 'la'.
'fool' becomes 'con'.
'in charge' becomes 'ic'.
'la'+'con'+'ic'='LACONIC'
'of' acts as a link.
(Other definitions for laconic that I've seen before include "with little expression" , "Saying little" , "Using few words, terse" , "Curt in conical way" , "like a man of few words" .)