Emblem of French depravity (6)
I believe the answer is:
device
'emblem' is the definition.
(device is a kind of emblem)
'of french depravity' is the wordplay.
'of french' becomes 'de'.
'depravity' becomes 'vice' (I've seen this before).
'de'+'vice'='DEVICE'
(Other definitions for device that I've seen before include "Scheme for achieving something, or a trick" , "Heraldic emblem" , "Gadget, tool, piece of equipment" , "Plan, scheme, trick" , "Gadget, piece of apparatus" .)