Final answer:
The poetic device used is onomatopoeia, with the word 'clattered' mimicking the sound of the seconds moving out of the ring.
Step-by-step explanation:
The poetic device used in the given sentence is onomatopoeia. Onomatopoeia refers to the use of words that imitate sounds associated with the objects or actions they refer to. In this sentence, the word 'clattered' imitates the sound of the seconds (the people who assist the boxers) moving out of the ring.
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