Rule again, suffering spasmodic pain (9)
I believe the answer is:
neuralgia
'spasmodic pain' is the definition.
'rule again suffering' is the wordplay.
'suffering' indicates an anagram.
'rule'+'again'='ruleagain'
'ruleagain' with letters rearranged gives 'NEURALGIA'.
(Other definitions for neuralgia that I've seen before include "Sharp pain extending along nerves" , "Pain from damaged nerve" , "illness" , "sort of pain" , "Shooting pains" .)