Possible Clues:

• Bearing of ship bound for the Antarctic
• Last to be first in this test
• Ability to withstand hardship for long periods
• Struggling near-dunce shows staying-power
• Nude dancing career involves new stamina
• Last to be first in this test?
• Creed a nun translated showing persistence
• Last to demonstrate this?
• Stamina of final United contest holding Everton finally
• Staying power of English knight Mussolini managed to get imprisoned