Possible Clues:

• "Shucks"
• Beaver Cleaver expletive ... or what you might need to be to answer 18-, 23-, 51- and 60-Across?
• Interjection expressing surprise
• "Gosh!" (or, based on the starts of starred answers, one who is expert at solving this puzzle's theme?)
• 'Wow, you're a regular expert at turning left!'
• Expression of admiration
• Gracious medic leaves gadget outside small west-facing hospital
• "Imagine that!"
• 'Wow!'
• "Aw, shucks"