Clearly we need to avoid a diamond loser.
But there is no need to take any chances. We can dispose of the losing diamond on a winning club.
So, draw trumps and set up the clubs (by first leading the queen to avoid a blockage). Even if defenders hold up the ace until the second round, we still have the ♦A as an entry to dummy's club winner.
If we try instead to ruff the losing diamond with dummy's short trumps, we would suffer an over-ruff by South, and go one off.
