Possible Clues:

• Feudal Japanese leader
• Japanese governor
• Turn back inside to avoid contact with ruler
• Japanese commander gets control in a day
• Display firearm, say, to Clavell's governor
• Hereditary army commander in feudal Japan
• A question concerning its breeding gave Bassanio a hint
• Former military governor of Japan
• Just for fighting display for service with 21 across?
• An exhibition weapon from Japan, by the sound of it