Tempo is an important issue when it comes to declarer play and defense. It can be strange how much it can change when the timing in the play hits the actual layout of the cards.
Try your way as declarer in 3NT as north on the lead of the ten of clubs,5, 6 and now you are in charge.
Make your plan on the further play, if you let the ten hold the first trick east continue with a low club to the jack.
Have you found the making line?
I hope you let the ten hold the first trick, if not you let west find a expert defense. Winning the king of clubs, you lead a diamond to the queen followed by a heart to the jack. Your next move is the diamonds, west discard the 5 and jack of spades.
The position comes down to this when the fourth diamond is on the table, west is still to find a discard
West finds the perfect solution when he discards the jack of clubs. When you play a spade to the king and ace west just underlead a club to the nine. East grabs the diamond then play a club. West brings you down to 8 tricks by winning the ace and queen of clubs.
Lets take a look at the position when you hold back the king at first trick. East continue a club to the jack and the king. You stick to the same plan playing a diamond to the queen then a heart to the jack. But now the tempo has changed by a trick.
When you grab the diamonds, the position looks like this when west has to find a discard
He has to discard a club, but now the option to underlead a club to the nine wont work since east only has the singleton nine.
It was all about the tempo, give a way a trick and the defense lost their chances.