Straightforward bidding gets East-West to 4♠ and then the fun starts.
Declarer can see 9 tricks (5 Spades, 3 Hearts, and the ♦ A) but needs a tenth. So much depends on the lead.
If South leads a Club then declarer can assume that North has the ♣ A (who would underlead an Ace against a suit contract), play the ♣ J which brings out the ♣ A and makes Dummy's ♣ K the tenth trick.
South shouldn't lead a Diamond as leading from Q x x is likely to give a trick away but if they do then Declarer lets the defence win that trick and then when next in, which won't be long, cashes the ♦ A and ruffs a third round of diamonds for the tenth trick.
A Spade lead by South should be won by declarer before playing ♦ A and exiting with a Diamond, setting up the Diamond ruff as the tenth trick.
If South leads the ♥ A followed by their second Heart declarer cannot afford to try and set up the Diamond ruff as North will play a third Heart for South to trump when they get in with the ♦ K. Declarer must draw trumps first and then is left with three Diamond losers and a Club loser but can only afford to lose two more tricks.
The Heart lead puts declarer on a guess as to whether they make 4♠ or not which is much better for the defence than the other leads which mean the contract always makes.
Declarer must play Clubs before Diamonds because it is vital to keep the ♦ A to prevent the defence cashing Diamond winners when they get in, and declarer needs to play low towards Dummy and play the ♣ J rather than the ♣ A to make their contract.
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