Revolutionary against Republican performing V-sign? (7)
I believe the answer is:
chevron
'v-sign?' is the definition.
(I've seen this before)
'revolutionary against republican performing' is the wordplay.
'revolutionary' becomes 'che' (Che Guevara the Marxist revolutionary).
'against' becomes 'v' (abbreviation for 'versus').
'republican' becomes 'r' (abbreviation).
'performing' becomes 'on' (as in being on stage).
'che'+'v'+'r'+'on'='CHEVRON'
(Other definitions for chevron that I've seen before include "V-shaped sleeve badge" , "Stripes" , "V-shaped insignia" , "V-shaped band" , "pointed symbol" .)