French article put in after gag (7)
I believe the answer is:
silence
'gag' is the definition.
(I know that gag is a more specific form of the action silence)
'french article put in after' is the wordplay.
'french article' becomes 'le' (definite article in French).
'put in' is an insertion indicator (back).
'after' becomes 'since' (since can mean after a certain time).
'le' placed within 'since' is 'SILENCE'.
(Other definitions for silence that I've seen before include "It is golden, they say" , "Quietude" , "may be required in court" , "Soundlessness" , "Gag" .)