Source: January 2015 ACBL Bridge Bulletin 
South opened 1 and ultimately played in 4 .
West led the A, followed by the A and then led the K, tapping the dummy. It’s right to draw trumps, and South started to do that. The Q and J revealed that West started four to the 10, and East started with a singleton.
How should South continue? It seems obvious to cross to the K, then draw trumps and take the rest with the spades. Do you see a danger? Here are some things to think about if you’re South: How many diamonds does West have? Very likely he has six. How many hearts does West have? He has four. It is fairly certain that West started with three black cards. He might have had only two if he had seven diamonds. This all suggests that West’s A was a singleton.
If you try to come to your hand with a club, West will ruff and lead a spade. You won’t be able to get rid of your club losers on the spades because West still has a trump. If you think these dangers are real, what can you do to overcome them? Can you make 4?
The answer is this: When you play the second heart from dummy and see East show out, overtake with your king. Continue with the ace and give West his trump trick. This line costs you a trump trick, but you gain two other tricks in return. Whatever West does, you can win and claim. You will have four spade tricks, four heart tricks, one diamond ruff in dummy and one club trick.
Here is the complete deal:
On this layout, your play is necessary. At matchpoints, this situation is hard on the nerves because you might have 11 tricks if West has a second club.