Possible Clues:

• Grin about one happy as sandboy?
• Grin about setter's figure of speech
• As blind as a bat, e.g.
• 'Clean as a whistle,' e.g
• ''Cool as a cucumber,'' for one
• Joyful expression encapsulating the author's particular way with words
• High as a kite, e.g
• "Happy as a clam" or "mad as a wet hen"
• 'Sharp as a tack,' for example
• "Snug as a bug in a rug," e.g