Possible Clues:

• Island inhabited by a single soldier
• Klink, e.g.
• Officer's sound heart
• A bit of guts shown by the Spanish officer
• Sounds as if the officer is at the centre of things
• With 50-Across, he started a fast-food franchise at age 65
• Does rank enable him to be at the heart of thigs, by the sound of it?
• Blimp or Klink
• One has a rank sort of middle, by the sound of it
• Rank enough to be at the heart of things, by the sound of it