Pulse in broth that needs stir (5)
I believe the answer is:
throb
'pulse' is the definition.
(synonyms)
'broth that needs stir' is the wordplay.
'that needs stir' is an anagram indicator (I've seen 'needs stirring' mean this (I've seen this in other clues)).
'broth' with letters rearranged gives 'THROB'.
'in' acts as a link.
(Other definitions for throb that I've seen before include "Vibrate with rhythm like heart" , "Drum" , "beat repeatedly" , "Sound of engines" , "Broth (anag.)" .)