Possible Clues:

• Sounds like the officer at the heart of the corps
• Thing on a corncob
• Core of a computer's operating system
• Report of senior officer — a bit of a nut!
• Cob growth
• Officer reportedly shows soft heart
• Report of officer in centre of Brazil?
• Part of vessel occupied by navy, in essence
• Essence of report of army officer
• Pop Secret tidbit