Trial — result of whiplash? (4,2,3,4)
I believe the answer is:
pain in the neck
I believe this clue is a double definition.
'trial' is the first definition.
(both can mean a source of annoyance)
'whiplash?' is the second definition.
(whiplash may cause neck pain)
'result of' acts as a link.
(Other definitions for pain in the neck that I've seen before include "Really annoying person" , "Troublesome person or thing" , "Torticollis" , "Annoyance (colloq.)" , "Very tiresome person or thing" .)