Related Clues:

• A river, on reflection, is a river
• Annoyed exclamation raised about the old person hanging on
• Guy about to make a comeback, a tenacious sort
• Tenacious steed brilliant when carrying you
• One likely to carry on being stumped by philosopher
• One with lasting qualities
• Philosopher on the street is one unlikely to give up
• Lead actor grips you, being in for the long run
• Stumped by philosopher, I won't quit
• One keeps going way over philosopher's head
• One with stamina
• Stumped by philosopher, one's unlikely to give up
• Celeb entertaining the old: one with enduring qualities
• A horse that's better in the long run
• Not a drop-out in the long run