French from over Channel take off (6)
I believe the answer is:
deduct
'take off' is the definition.
('deduct' can be a synonym of 'take off')
'french from over channel' is the wordplay.
'french from' becomes 'de' ('from' in French).
'over' says to put letters next to each other.
'channel' becomes 'duct' ('duct' can be a synonym of 'channel'**).
'de'+'duct'='DEDUCT'
(Other definitions for deduct that I've seen before include "Remove" , "Withhold" , "Subtract, take away" , "Make a subtraction" , "Knock off" .)