Dresses tart, exquisite but not a revolutionary (11)
I believe the answer is:
robespierre
'revolutionary' is the definition.
(French revolutionary Maximilien Robespierre)
'dresses tart exquisite but not a' is the wordplay.
'dresses' becomes 'robes' (robing is a kind of dressing).
'tart' becomes 'pie' (both are baked goods).
'exquisite' becomes 'rare'.
'but not' indicates named letters should be taken away.
'rare' with 'a' taken out is 'rre'.
'robes'+'pie'+'rre'='ROBESPIERRE'
(Other definitions for robespierre that I've seen before include "leading figure in French history" , "Revolutionary leader" , "French revolutionary who was guillotined" , "French Jacobin leader, guillotined in 1794" , "old revolutionary" .)