Find fault with a revolutionary's grand manner (7)
I believe the answer is:
panache
'grand manner' is the definition.
(I've seen this before)
'find fault with a revolutionary's' is the wordplay.
'find fault with' becomes 'pan' (panning is a kind of finding fault with).
'revolutionary' becomes 'che' (Che Guevara the Marxist revolutionary).
'pan'+'a'+'che'='PANACHE'
(Other definitions for panache that I've seen before include "Great style" , "Sense of style, swagger" , "Swagger; theatricality" , "'Dash, flair (7)'" , "stylish carriage" .)