When I was learning bridge one book did more to improve my game than other. It was Killing Defence at Bridge- by Hugh Kelsey.
Many of the deals are difficult but careful study of them will improve your defense. In particular, Kelsey stresses counting. Today’s deal the second in the book is one that many players would misdefend. The bidding follows British lines, the author being Scottish. The opening bid of one heart promises only a fourcard suit.
West’s opening lead is unmistakably a singleton. Most Easts would win trick one with the A and immediately give partner a club ruff. However, that would be the end of the defense. East gets his heart king, but declarer’s spade losers disappear on dummy’s clubs. East can see three defensive tricks: the heart king, the club ace and a club ruff. He must ask himself where the fourth will come from.
If West has an ace there is no problem. But if West has the spade king, it is imperative to switch to a spade now, at trick two. That establishes the spade king as a winner. West, who must have three hearts, can be given his club ruff when East gets on play with the heart kin. When on defense. always remember your target: the number of tricks you need to defeat the contract.