North opened 1♣. After complaining of not having a good hand since 2008, South has a great hand, and slam looks likely when partner opens. South considered replying 2♦, then went for 1♦. North rebid 2♣ and South made a forcing 2♠ bid. There was then a bit of confusion as North-South realised they already had sixty towards a part score (this was rubber bridge), but North was convinced to bid on with the chance of a slam, so went for 2NT. With the lunch break nearly over, South agreed to bid 6♦.
Looking at the South hand there's not many losers. What you're looking for in dummy is cards to take care of your losers. So the ♣A is great, and so is the ♥K. Those are the only useful high cards though, and unfortunately dummy has nothing in Diamonds, but has two of them at least.
West lead a Spade, won by declarer's Ace. The defence are now threatening to take a Spade trick. You have two extra winners in dummy (the ♣K and ♥Q), which you can use to throw away two of your Spades, but unfortunately not three. If you could set up one of dummy's Clubs in time to throw away another Spade that would be good, but unfortunately there's not enough entries to dummy. So you're going to have to lose a Spade. That means that to make the contract you need no trump losers.
The normal play in that Diamond suit, with eight of them missing the Queen, is to finesse (Eight ever, Nine never). It's worth starting with one high Diamond first though, just in case there's a singleton Queen. So declarer played the ♦A, crossed to dummy in Hearts, and finessed. When West won the ♦Q the contract was one off.