Brief the French against being in charge (7)
I believe the answer is:
laconic
'brief' is the definition.
('laconic' can be a synonym of 'brief')
'the french against being in charge' is the wordplay.
'the french' becomes 'la'.
'against' becomes 'con' (I've seen this before).
'being in charge' becomes 'ic'.
'la'+'con'+'ic'='LACONIC'
(Other definitions for laconic that I've seen before include "like a man of few words" , "Tersely spoken" , "Terse - can coil (anag)" , "not saying much" , "Concise - terse" .)