Related Clues:

• Like Homo habilis
• Not at ease, perhaps
• Entranced
• Be constructive?
• Captivated
• Build an edifice
• Put up, as a building
• Hanging on every word
• Having good posture
• Glued to the tube
• Very attentive
• Upright, as posture
• Straight up and down
• On twos, rather than fours
• Fully absorbed