Dealer North. E/W Vul.
Lead: King of Hearts for dummy’s seven, your eight and declarer’s Ace.
How many points should your partner have?
17 HCP (North) + 9 HCP (you) + 8-10 HCP (South bid again after 3♦) = 34-36 HCP, which leaves abouth 5-6 HCP for partner of which you already know almost all in the form of King-Queen of Hearts.
Looking at your hand, which honors should declarer hold?
The two major-suit aces and maybe the Club Jack, at least fifth.
Why at least fifth?
Simply because with his response of 1NT he has stated that he has less than four cards in each major and you also know that he cannot have more than two Diamonds (a 5-3-3-2 distribution). By the way, he starts tackling the Clubs by playing the seven from his hand to West’s five and North’s King.
Do you take it?
Yes, witout hesitation. South has doubtlessly played his smallest Club (J10987) and you must not duck the King because – for the moment – the suit is blocked by the Queen.
Is he about to win his contract?
Assuming he has a potential of four Club tricks to which you can add the two aces in the majors and Ace-King-Queen of Diamonds (even if a bad surprise is waiting for him in the form of the 5-1 break), he will be able to rapidly claim nine tricks…
Unless you have the courage to deprive him of his only entry to his hand, the Spade Ace, by playing the Spade King after the Club Ace, because after all you won’t beat Three No-Trump with West’s Hearts.