A leading Roman? (9)
I believe the answer is:
centurion
'a leading roman?' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for centurion that I've seen before include "Commander in ancient Rome" , "Leading Roman" , "Nocturne I played for old Roman army officer" , "roman soldier" , "Roman leader of 100 soldiers" .)