You are playing a weak NT system, so N is either unbalanced, or 15-17 (or 18-19) balanced. Opponents lead the ♠4, playing UDCA, 3/5 leads; W follows with the T of spades to the first trick. If you lead toward the Q of diamonds at any point, or lead the Q of diamonds from the board, W takes his ace & returns a spade. E plays the T on the first round of diamonds.
First, do you want to be in this slam?
2nd, plan the play.
CSGibson writes "You are playing a weak NT system, so N is either unbalanced, or 15-17 (or 18-19) balanced. Opponents lead the ♠4, playing UDCA, 3/5 leads; W follows with the T of spades to the first trick. If you lead toward the Q of diamonds at any point, or lead the Q of diamonds from the board, W takes his ace, RHO playing the T on the first round.
First, do you want to be in this slam? 2nd, plan the play.
IMO, Slam seems OK. My guess: ♠A, ♦QK .If both follow low, then a third ♦, (because they are likely to be 3-3).