Possible Clues:

• Pay attention to The Last Word - it's the epitome of deep thought
• Focus on The Last Word is reduced
• Paid attention as to not lose Focus on back road
• Neat, undiluted
• 63 + 64 + 65-Across
• Deep Thought?
• Focused - made denser
• Deep thought
• Focused on trick to get money calculated
• Paid attention to focus on The Last Word