Sentence:  Then I played on diamonds, to <WSD>ruff</WSD> out the suit – but East had four diamonds and West none, so I had annoyingly to lose a trick to East's ♣K in the end. 
Meaning of the word marked with <WSD> tags:  "Especially in the form" '''ruff out''': to defeat (a card, etc.) by ruffing, thus establishing the master card in the suit led.