Possible Clues:

• ''Let me sew you to your sheet,'' e.g.
• Lack of pies, say
• Is bird-watching an appropriate example of this?
• 'Mean as custard' for 'keen as mustard', say
• Silly sound transposition
• Promise son to get treatment for speech defect
• Dean's remark initially modified
• 'A lopping of sweaters', for example
• That half-warmed fish, for example
• An initial mistake