Saviour cures mad queen (7)
I believe the answer is:
rescuer
'saviour' is the definition.
(I know that saviour can be written as rescuer)
'cures mad queen' is the wordplay.
'mad' is an anagram indicator.
'queen' becomes 'er' (abbreviation for Elizabeth Regina).
'cures' is an anagram of 'rescu'.
'rescu'+'er'='RESCUER'
(Other definitions for rescuer that I've seen before include "One who saves from a dangerous situation" , "One who delivers" , "Person bringing one out of danger" , "Saviour" , "freer" .)