Possible Clues:

• -- Ryan, character played by Brad Pitt in the 2004 film 'Ocean's Twelve'
• Out of practice, head of firm's removed
• Copper dependable? Not at first
• Like old metal outdoors
• Easily irritated principal's dropped out of practice
• Out of practice, but reliable (just missing start)
• Out of practice, strong opener's dismissed
• Cantankerous head dismissed, not employed for some time
• Out of practice in game, feisty after first half
• Reliable prisoner loses head, being out of practice