Possible Clues:

• Inflexible soldier in free housing
• Hard to fake passport
• Infrangible
• Frozen, having died on Swiss mountain
• Fix it up, so I would, for a big stiff
• Stiff and inflexible
• It's hard to fit this out before I would
• Clothes I had starched too much?
• Inflexible outfit I associated with duke
• Firm's attire starts to irritate directors