Stoker suffered a blow (6)
I believe the answer is:
stroke
'a blow' is the definition.
(I've seen this before)
'stoker suffered' is the wordplay.
'suffered' is an anagram indicator (I've seen 'suffering' mean this).
'stoker' with letters rearranged gives 'STROKE'.
(Other definitions for stroke that I've seen before include "Fondle - rower" , "Gustav --, composer" , "Brain haemorrhage or caress" , "Stoker (anag.)" , "A blow or brain seizure" .)