Sentence:  In any inquiry into the way in which great literature affects the emotions , particularly with respect to the sense of harmony , or <WSD>relief</WSD> of tension , or sense of `` a transformed inner nature '' which may occur , a most careful exploration of the particular feature of the experience which produces the effect would be required . 
Meaning of the word marked with <WSD> tags:  the act of reducing something unpleasant (as pain or annoyance)