The French caught by true form of sermon (7)
I believe the answer is:
lecture
'sermon' is the definition.
(I've seen this before)
'the french caught by true form' is the wordplay.
'the french' becomes 'le' ('the' in French).
'caught' becomes 'c' (cricket abbreviation).
'by' is a charade indicator (letters next to each other).
'form' indicates anagramming the letters (another form of the letters).
'true' is an anagram of 'ture'.
'le'+'c'+'ture'='LECTURE'
'of' acts as a link.
(Other definitions for lecture that I've seen before include "Teaching discourse" , "An instructive talk, in school or church" , "Educational talk" , "Deliver a talk" , "Sermon" .)