Possible Clues:

• Something requiring a snap decision
• When two fairly matched cameramen raced, it came down to a ..
• Close race ending, and a hint to the answers to 17-, 26-, 39- and 54-Across
• Sporting moment captured in glossy perhaps?
• *Tight race climax
• End of exciting race, still perfect
• Close contest in public house, too tricky too deal with
• Climax that's close, if in posh hot pants
• End of a close race
• O?