As is the modern style, West led a third- (or fifth-) highest ♦2. East wins the ♦Q and continues with the ace and king of the suit. You ruff with the ♠10 and draw three rounds of trumps. So far, so good. How do you plan to get to 10 tricks from here?
After ruffing the diamond and playing three rounds of trumps, declarer played a club to dummy’s queen, East winning with the ace and exiting with a low club to dummy’s jack. Declarer then played a club to his king, noting that East had at least three clubs. As East/West were playing five-card majors with a 15-17 1NT opener, declarer inferred that East could not have the ♥Q if he had started with a balanced hand. If East had an unbalanced hand, then, of necessity, he would have started with 3=1=5=4 shape. With that in mind, declarer decided that there was no point in playing a heart to the ace and finessing the jack on the way back. If the contract were to succeed in the former case, declarer needed East to have a doubleton ♥10. In the latter case, he could make 10 tricks only if East started with a singleton queen or ten in the suit. So, declarer cashed the ♥K and advanced the ♥J. After West played low, declarer played the 9 from dummy and the ♥J won the trick, pinning East’s doubleton 10. The full deal: