Possible Clues:

• Last longer than
• The 'last longer' overall?
• In a bout we are able to last longer
• 'Exhaust such non-underclothing, perhaps (7)'
• Last longer, not in what you put on
• Be more durable than
• Not in constant use, so last longer
• Perhaps it's not underclothing one will use up
• Get too big for one's boots?
• Last longer than English in blooming conflict!