Runner perhaps that speeds up in excitement? (5)

I believe the answer is:

pulse

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'excitement?' is the definition.
(I've seen this before)

I don't understand the remainder of the clue.

(Other definitions for pulse that I've seen before include "Musical beat; edible seeds" , "enjoyed by vegans?" , "Bean - throb" , "Excitement" , "Arterial throb" .)

I've seen this clue in The Sun.

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