Revolutionary support about to be attached to dresses (11)
I believe the answer is:
robespierre
'revolutionary' is the definition.
(French revolutionary Maximilien Robespierre)
'support about to be attached to dresses' is the wordplay.
'support about' becomes 'pierre' (I can't justify this - if you can you should give a lot more credence to this answer).
'to be attached to' is a charade indicator (letters next to each other).
'dresses' becomes 'robes' (robing is a kind of dressing).
'pierre' put after 'robes' is 'ROBESPIERRE'.
(Other definitions for robespierre that I've seen before include "Revolutionary leader" , "French revolutionary who was guillotined" , "French Jacobin leader, guillotined in 1794" , "leading figure in French history" , "old revolutionary" .)