Policeman has one but may not take it, on the beat (5)

I believe the answer is:

pulse

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'the beat' is the definition.
(synonyms)

I don't understand how the rest of the clue works.

(Other definitions for pulse that I've seen before include "often sought medically?" , "Seed of bean or pea plant" , "Musical beat; edible seeds" , "Healthy food" , "Heart beat - peas, beans etc" .)

I've seen this clue in The Irish Independent.

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