Sack belonging to French model (6)
I believe the answer is:
depose
'sack' is the definition.
(I've seen this before)
'belonging to french model' is the wordplay.
'belonging to french' becomes 'de' ('of' or 'belonging to' in French).
'model' becomes 'pose' (model can mean to pose).
'de'+'pose'='DEPOSE'
(Other definitions for depose that I've seen before include "Remove from office or position" , "Dethrone; bear witness" , "Set down" , "Remove a ruler from office" , "Attest and force off a throne" .)