After taking the first trick with dummy's bare Diamond ace you take stock making sure you notice West not following suit to trick One.

Without doing any work you now have 9 winners- 3 top spades, 1 Diamond and 5 Clubs.

Where will a 10th trick come from? Guessing the Hearts correctly if at all? There is a much safer way to establish the 10th trick.

All you have to do is come to hand via a Club and work on establishing one extra diamond trick. (not usual to establish an extra trick in the suit that the opposition has led but it works here. If you do this, you know West, the safe hand as far as the Heart suit is concerned. will gain the lead and be unable to play a Heart without giving you a 10th trick there. West gets off lead with a Spade which you win in hand before playing a third Diamond. Now your ♦9 is established. and you will make 10 tricks i.e 3 Spades, 2 Diamonds and 5 clubs.