Possible Clues:

• Navy divides part of ship, in essence
• Most important part
• Does it sound so rank at the heart of things?
• The heart of a military officer, say
• Sounds as if one might get over the core, by the sound of it
• One sounds so rank in the middle of the corps, by the sound of it
• Contents of shell
• What sailors are to boat here
• Sounds as if one is too nutty for command
• Essential part of something an officer mentioned