Suffering? Current back spasm ruled out (7)
I believe the answer is:
illicit
'ruled out' is the definition.
(thesaurus)
'suffering? current back spasm' is the wordplay.
'suffering?' becomes 'ill'.
'current' becomes 'i' (symbol for electric current).
'back' says the letters should be written in reverse.
'spasm' becomes 'tic' (tic is a kind of spasm).
'tic' reversed gives 'cit'.
'ill'+'i'+'cit'='ILLICIT'
(Other definitions for illicit that I've seen before include "not conforming to regulations" , "Bootleg; clandestine" , "Not legal" , "Contraband" , "Prohibited" .)