Military leader and Roman emperor beheaded Roman orator (6)
I believe the answer is:
cicero
'roman orator' is the definition.
(Cicero was a Roman politician)
'military leader and roman emperor beheaded' is the wordplay.
'military leader' becomes 'CIC' (abbreviation for commander in chief).
'and' is a charade indicator (letters next to each other).
'roman emperor' becomes 'Nero' (Roman emperor, 37-68 AD).
'beheaded' means to remove the first letter (the head of the word is removed).
'nero' with its first letter taken off is 'ero'.
'cic'+'ero'='CICERO'
(Other definitions for cicero that I've seen before include "Philosopher" , "Roman orator; type size above pica" , "accomplished orator" , "Orator's" , "Famous Roman orator" .)