In 5D, it seems like declarer might be able to pitch losing clubs on spades. The problem is a lack of entries to the north hand. Declarer has to take his spades after the trumps are drawn, and must ruff the heart loser before the trumps are drawn. The defense has no way of keeping declarer from scoring three spades, a heart, four diamonds and two clubs. Their best bet is to try to force declarer with hearts.
Timing is everything.
T973 Declarer doesn't mind losing a second heart, pitching a club, but if east wins the third round and leads the fourth declarer is stuck. The trick, then, is to lose the two heart tricks early, to cut off the entry to east's hand. If west leads the ten or three of hearts, declarer plays low from dummy. Say west continues hearts. Declarer covers, and if east ducks, declarer immediately exits with a heart, pitching a club from hand.