Food is something you'd be dead if you didn't have (5)

I believe the answer is:

pulse

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'food' is the definition.
(pulse is a kind of food)

I can't explain the rest of the clue.

(Other definitions for pulse that I've seen before include "When you're gone, you haven't one" , "Rhythmic throb" , "Series of rhythmic beats" , "Heart beat - peas, beans etc" , "Healthy food" .)

I've seen this clue in the Evening Standard.

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