Possible Clues:

• Long-distance runner, rather than sprinter
• One still in the game, in poker
• Yes, it's no go for the rat
• Tabloid accepts the old one has stamina
• Person who lasts the course, doesn't quit
• Street philosopher one unlikely to give up
• One that can last the course
• Supporter in the long run?
• Tenacious steed brilliant when carrying you
• One hanging around