Sentence:  Recently he had successfully concluded a case featuring a poet who wore only latex, lived on liquorice allsorts and worshipped a horse she believed to be the reincarnation of Radclyffe Hall. And she was the <WSD>straight man</WSD>. 
Meaning of the word marked with <WSD> tags:  A member (of any gender) of a team of comic performers who plays a supporting role by helping to set up jokes and punch lines through engaging in dialog with another comedian playing a more eccentric or otherwise more interesting character; a foil who plays such a role in theatrical comedy.