Possible Clues:

• Brook or lake fish
• Fish (associated with Schubert?)
• Turkey not in fashion? Get fish
• "Rainbow" swimmer
• Time to defeat an unpleasant old woman?
• Fly-fishing target, perhaps
• Swimmer’s time leading to defeat
• Vonnegut's Kilgore
• Swimmer that strong needs to produce air
• … fish from the River Ouse, until tickling starts