Saviour (8)
(Other definitions for rescuer that I've seen before include "One who delivers" , "One who saves someone" , "One who saves from a dangerous situation" , "One who saves another from peril" , "Saviour" .)
(Other definitions for white knight that I've seen before include "Heroic champion (of the chessboard?)" , "Someone coming to the rescue" .)
'saviour' is the definition.
(I know this)
This is the entire clue.
(Other definitions for redeemer that I've seen before include "Mere deer for the saviour" , "One saving another from sin" , "One who saves (another) from sin" , "One who saves (sinner)" , "Christ, who saved us from damnation" .)