Possible Clues:

• Bogeyman
• Potter of "M*A*S*H," for one
• One in the corps sounds like one at the core
• 'No cello for this officer, strangely (7)'
• Officer's unit left behind mountain pass
• 'It's rank at the heart of the nut, by the sound of it (7)'
• Commander
• Sounds as if one is in the middle rank
• By himself in the pass, it sounds as if he's at the centre of things
• One is in the lead, but it sound in the middle