Possible Clues:

• Rock singer repelled servant on first of December
• No heart: might such a person be rough?
• The hardest thing before match — it's achieved years later
• Hardest substance
• No servant recalled duke, a very special chap
• No heart, such a person might be rough!
• Stone in part of baseball playing area
• No servant upset duke? Brilliant!
• Odd man out: one must enter playing field
• Area on sports field that is very hard