Sentence:  "The position you'd put me in would be this—of playing a game—and a jolly important game at that—in which the loser loses to me on purpose. . . . If we're going to play a game," he continued, addressing Davenant, before the latter had time to speak, "for Heaven's sake let us <WSD>play it straight</WSD>—like men. Let the winner win and the loser lose—" 
Meaning of the word marked with <WSD> tags:  To behave in a manner that is straightforward, honest, or sincere.