Saviour, concerning terrible curse (7)
I believe the answer is:
rescuer
'saviour' is the definition.
(I know that saviour can be written as rescuer)
'concerning terrible curse' is the wordplay.
'concerning' becomes 're' (both can mean on a particular topic).
'terrible' indicates an anagram.
'curse' is an anagram of 'scuer'.
're'+'scuer'='RESCUER'
(Other definitions for rescuer that I've seen before include "One who saves from a dangerous situation" , "Saviour" , "One who saves someone" , "One who saves another from peril" , "One who delivers" .)