There was lots of bidding on this online deal. South held (vulnerable against not, team scoring)

 K6  
 K2  
 AK1083  
 AKQJ. His RHO opened 2 and he doubled. LHO raised to 3 and his partner doubled! That is a lot of bidding. Presumably the double showed "cards." South shrugged (well, I was West and couldn't really see any shrugs over the internet) and bid 6NT. He received a diamond lead and saw:
 

Vul:N-S Dlr: East	10984  A1084  J972  4
	K6  K2  AK10873  AKQJ

I don't think North has nearly enough for his double, but that's what he did. On the diamond lead, East played the queen. What is your plan? You have 11 top tricks (2 hearts, 5 diamonds and 4 clubs). Declarer went to dummy and led a spade to his king to try for his 12th trick. Do you like that plan?

It is simple, but rates to fail. Why? Why wouldn't West lead his partner's suit? If he had the queen, jack or small ones, that would be a standout lead. The only reason West would not lead a spade is if he had the ace. The auction indicates that the 6NT bidder has the king.

Accordingly, what is the plan? There was a lot of bidding going on, but the opponents were at favorable vulnerability. West wouldn't raise with a singleton, so likely the spades are 5-2. Why would East open with a so-so five-card suit? Likely he is very distributional. Is there any way to make the contract with the A with West?

Yes. Declarer should continue by running diamonds. The opening leader had three low diamonds and RHO a singleton Q. East discards some low clubs and low spades. West throws a club and a heart. Next, cash the top clubs. East turns out to have 5 of them. What does that mean West started with? You have a complete count and this is the full deal:

Vul:N-S Dlr: East	10984  A1084  J972  4
A7  J9765  654  1083		QJ532  Q3  Q  97652
	K6  K2  AK10873  AKQJ

After you take your 9 minor-suit winners, what can poor West keep? He must come down to 4 cards. If he ever throws a spade, you expect the ace is now singleton. You play the 6 and have 12 tricks. If West keeps both spades, that means he has to reduce to only 2 hearts, and now the hearts provide declarer with his contract.

This is called a "squeeze without the count" -- not something I would consider "Intermediate." However, with a little card placing (the opening lead marked the A) and some counting, this contract was makeable.