Possible Clues:

• Orator's challenge
• Suffer with sibilants
• Issue for a speech coach, perhaps
• Sigmatism, by another name
• A speech affliction
• Struggle with sassafras?
• One reason for speech therapy
• 'With ____ of leaves and ripple of rain' (Thwinburne)
• Struggle with scissors?
• Struggle with one's sins?