Against your slam, West – no doubt envisioning club shortness in the North hand based on the jump to 6♦ – starts off with a trump. What is your plan for bringing this contract home?
West’s lead was good for his side. On other leads, (especially a club), South would have been able to ruff three clubs in dummy and make 12 tricks on most defensive layouts. While he could have relied on spades being 3-3 or a major-suit squeeze, declarer decided that setting up dummy’s hearts offered a brighter prospect of success.
After taking the opening lead with dummy’s ♦10, declarer made the key move of ruffing a heart high in his hand. After ruffing a club in dummy and a second heart high in hand, declarer crossed to dummy by playing a low spade to dummy’s ace to lead a third round of hearts. When East discarded a club from hand, so did declarer, which proved to be necessary to make 12 tricks, for otherwise he would have lost trump control.
West took the trick with the ♥Q and exited with a trump to dummy’s 9 and declarer’s 3. After ruffing another heart, thereby establishing the suit, declarer drew West’s remaining trump with his ♦A, then claimed his contract: He made three spades, two hearts, six trumps and a club ruff for a total of 12 tricks.
Observe that, after West had won the ♥Q, he had no winning defense. A spade, his best play in abstract, would have been won in hand with the queen and dummy would have been entered by playing a spade to dummy’s king, after which the rest of the play would have been as above. A club exit would have fared no better: declarer would have ruffed in dummy, ruffed a heart low, drawn trumps, then claimed the rest of the tricks. The full deal: