Prince not quite competing with King after support for filibuster, once (9)
I believe the answer is:
privateer
But I can't explain it at all! Could you help me understand?
(Other definitions for privateer that I've seen before include "Pare rivet down for a ship authorised to make war" , "Non-naval vessel of old, licensed to attack" , "Non-government owned warship" , "Armed ship used in war but not government-owned" , "Sailor may go on it" .)