In the trump suit, he might lose one, two or no tricks, depending on how the defenders’ cards are divided. South should start by taking the spade lead with the ace and promptly return a spade. Then, after playing a club to the king, South ruffs dummy’s fourth spade, finally establishing the ten as a trick. If West elects to ruff with the jack at this point, declarer can discard dummy’s diamond, so let’s say West discards a diamond. South ruffs the club and discards his diamond on the ten of spades.