This deal had a neat point, easily overlooked in the heat of the moment. We are not told the bidding (perhaps the authors, like me, could not think of a plausible sequence) but South ended in Six Diamonds - clearly an excellent contract. Life would have been easy on any other lead, but West found the most worrying one of a heart.
Clearly trumps could not be tackled immediately, but things started well when three rounds of clubs stood up and dummy's heart loser went away. With a sigh of relief, declarer started on trumps, but West won the first round and unsportingly led a fourth round of clubs, allowing his partner to score the setting trick with the ten of diamonds.
This was an irritating setback, but an unnecessary one. To bypass East- West's defensive opportunity, declarer (once the heart loser has gone away) should ruff a heart on table and cash the ace of spades, discarding his remaining top club. Then, and only then, can he play trumps safely.