Deceived the French teacher (3,2)
I believe the answer is:
led on
'deceived' is the definition.
('lead on' can be a synonym of 'deceive')
'the french teacher' is the wordplay.
'the french' becomes 'le'.
'teacher' becomes 'don' (don is a kind of teacher).
'le'+'don'='LED ON'
(Other definitions for led on that I've seen before include "was encouraging" , "Beguiled" , "deceived" , "Unwisely enticed" , "Persuaded - tricked" .)