Possible Clues:

• Sun newspaper worker, one promising a fast run?
• Athlete -- small one making an impression
• One runs a short distance at top speed
• Second bookmaker's speedy runner
• He's quick enough for the type of work he does at last
• Athlete comes second to office worker
• He runs as fast as he can over short distance
• Fast type of work for one at last
• One moves quickly to attach second peripheral device
• Son given computer accessory gets one running