Declaring three no-trump on the club queen lead, declarer should look to the diamonds for his ninth trick. He can afford three losers, so his task will be easy on a 3-3 break.
South must therefore take measures to protect against a 4-2 diamond split.
If West has A-K-x-x, declarer must lead up to the queen, but this approach will fail when East has any honor-doubleton — and that holding is more likely than a small doubleton. It is best to duck the first diamond trick entirely and then continue by leading low again on the second round, thus smoking out honor-doubleton in either hand.
Declarer wins the club lead in hand, preserving entries to dummy, and then plays a low diamond. A surprised East wins with his eight and returns a club to the eight and ace. When declarer continues with a low diamond, East wins with the king (South discarding a spade) but can do no harm. Declarer wins the spade shift, say, crosses to the heart ace and leads out the diamond queen, pitching a heart to retain his club stopper. He wins the next spade trick, enters dummy with the heart jack and enjoys three diamond tricks. They come at the expense of two more heart winners, but that still makes nine.
East fares no better if he switches to spades at trick three. Declarer can succeed by winning, crossing to the heart jack and throwing a heart on the second diamond. If East continues spades, declarer takes it, crosses again in hearts and throws a club on the diamond queen. Thanks to South’s spade eight, the suit is blocked for the defense.