The average declarer begins today’s clubs by leading dummy’s queen. Quite correct if South needs only two club tricks. Likewise correct if South has the ten in one hand or the other.
In the actual hand, leading the queen loses two club tricks and the contract. It costs South nothing to lead the queen if the missing clubs divide 3-2: South wins two of the first three club tricks, and then his last club is good.
START WITH ACE
To allow for a 4-1 club break, South must take the ace of clubs (in case the singleton is the king) and then lead a club toward dummy in the hope that West has the king.
South must surely lose two tricks if East has four clubs headed by the king: but South loses only one club if West has the four clubs, as in today’s hand.
South leads clubs twice from his hand toward the queen-jack; dummy will get both the queen and the jack, and South get the ace.