Depose one French chair (6)
I believe the answer is:
unseat
'depose' is the definition.
(I've seen this in another clue)
'one french chair' is the wordplay.
'one french' becomes 'un' ('one' in French).
'chair' becomes 'seat' (something to sit on).
'un'+'seat'='UNSEAT'
(Other definitions for unseat that I've seen before include "Throw (as a 15?)" , "Remove from horse (or house?)" , "Dislodge from saddle" , "Remove from power" , "Get out of office" .)