No, it would not help for South to discard his remaining club, allowing East to hold the trick. East would return his spade and South would be compelled to ruff in his hand and then yield another trump trick. But the professor found a solution. He underruffed with his 5 of hearts!
With this coup, South escaped the end play and trapped East instead. If East returned a trump, South would finesse, draw the last trump and make dummy's good club. When, instead, East returned a spade, South let go his queen of clubs and ruffed the spade in dummy. With the lead coming from North at the 12th trick, South had the ace-jack of hearts behind East's king-8, and the contract was cold.