Mark Antony's second only to bloody revolutionary chief (9)
I believe the answer is:
commander
'chief' is the definition.
(I've seen this before)
'mark antony's second only to bloody revolutionary' is the wordplay.
'mark antony' becomes 'comma' (I can't justify this - if you can you should believe this answer much more).
'second only' becomes 'n' (ond letter of 'only').
'to bloody' becomes 'red'.
'revolutionary' is a reversal indicator (letters revolve around).
'red' in reverse letter order is 'der'.
'comma'+'n'+'der'='COMMANDER'
Can you help me to learn more?
(Other definitions for commander that I've seen before include "One hoping to be captain" , "Naval rank" , "leader" , "Chief" , "boss" .)