Pulse in broth that needs stirring (5)
I believe the answer is:
throb
'pulse' is the definition.
(I know that pulse can be written as throb)
'broth that needs stirring' is the wordplay.
'that needs stirring' is an anagram indicator (I've seen this in other clues).
'broth' with letters rearranged gives 'THROB'.
'in' is the link.
(Other definitions for throb that I've seen before include "Strong rhythmic beat" , "Beat rhythmically" , "Pound" , "One's heart may do it" , "Have strong or irregular heartbeat" .)