The opponents have been friendly, but don’t waste your good luck. You should play the ♣A next, followed by the ♣Q and ♣10 to drive out the jack, if it hasn’t already fallen. Win the return, draw the remaining trumps, if any, and run the diamonds, pitching the spade losers from your hand. The full deal:
At trick three, if you instead try a greedy low club to the king with the idea of returning to the closed hand with the ♠A to play the trump ace-queen, you might well discover that one defender began with J–x–x–x in trumps. When that defender gets the lead, he will cash a spade trick or two to defeat the contract. By giving up on 3–3 trumps, you guarantee that you’ll have no more than two losers: one heart and one trump.