Heath Robinson checks pulse (5)
I believe the answer is:
throb
'pulse' is the definition.
(synonyms)
'heath robinson checks' is the wordplay.
'checks' indicates a hidden word (check can mean to curb or restrain).
'THROB' is hidden in the letters of 'heath robinson'.
(Other definitions for throb that I've seen before include "Pound" , "Beat strongly" , "One's heart may do it" , "Broth (anag.)" , "Palpitate, quiver (with emotion)" .)