Face a revolutionary’s self-assurance (7)
I believe the answer is:
panache
'self-assurance' is the definition.
(thesaurus)
'face a revolutionary's' is the wordplay.
'face' becomes 'pan' (I've seen this in other clues).
'revolutionary' becomes 'che' (Che Guevara the Marxist revolutionary).
'pan'+'a'+'che'='PANACHE'
(Other definitions for panache that I've seen before include "A dashing manner" , "Great style" , "Style, elan" , "Flamboyant confidence" , "'Dash, flair (7)'" .)