Possible Clues:

• Part of A.A. Milne?
• Still with a chance to win
• Part of C.W. Post: Abbr.
• HST part, say: Abbr
• J. Edgar Hoover used one: Abbr.
• 'Put a sock --!'
• Abbr. part, often
• Vying
• Rolling __ (wealthy)
• Personal letter: Abbr.