Pulse starts to trouble husband resting on bed (5)
I believe the answer is:
throb
'pulse' is the definition.
(I know that pulse can be written as throb)
'starts to trouble husband resting on bed' is the wordplay.
'starts to' says to take the initial letters.
The first letters of 'trouble husband resting on bed' is 'THROB'.
(Other definitions for throb that I've seen before include "Strong rhythmic beat" , "Broth (anag.)" , "Palpitate, quiver (with emotion)" , "Martin -; Kingsley -" , "Beat quickly from excitement etc" .)