Possible Clues:

• Cotton material, turned and shortened, is shrinking
• Ill-defined personal appeal backs retiring
• Chickenhearted
• Some shot I middled in retiring
• Retiring in order, mainly, to pen note
• Lacking courage, I’m one hiding in study regularly
• In short spell, I had easily dominated
• Adjective for a mouse
• Shy and tiny character joined rejected girl
• Like Clark Kent