When my partner played this hand which I thought was relatively easy, he managed to go one off. Maybe he didn't count his winners and more importantly his losers

Initially after the lead and Spade switch he can now count 5 winners- 2 spades 2 Hearts and the Diamond Ace.,

What is the most important card in dummy- that Diamond Ace as it will be your entry to the.......established  Club Queen eventually.

On the losers front you have 2 Clubs, and 1 trump (as long as trumps break no worse than 3:2) and  1 spade.

After the lead, you know West has the Club King (as he led the Ace promising top of sequence). As long as you lead up to dummy's remaining Queen you will be able to establish the Queen to dispose of the Spade loser.

With all this in mind, win the second trick with the Ace and immediately play ONLY two rounds of trumps (Remember that "Rule of 1" - if there is one trump out higher than all yours no need to draw it as its a poor exchange rate 2 for 1) and it is so vital here not to play a third trump or the opposition will switch to a Diamond and remove your entry. UGH

After drawing only two rounds of trumps now play a club finessing West for that missing Club King. He takes the king and now you are home losing just one more trump trick eventually

You made 6 trumps,2 Spades,1 Diamond and 1 club.