Possible Clues:

• 'Think harder!'
• Concentration of force with company backed by United States
• Centre
• Prepare to shoot
• Commander in endless agitation in centre of activity
• Of course, Roe is missing from the centre of activity
• Concentrate on the house in front of me and you
• Point at which light rays converge or diverge
• Initially fix on centre, usually significant
• "Pay attention!"