The contract is notrump.

You need 4 tricks and you are willing to lose one trick to either opponent.

How do you play the spade suit?

Cash the ace and lead the 4 to the king. Then play the 10 or 9. This
produces four tricks if the suit breaks 3-3 or if the queen or jack
is doubleton.

Another Viewpoint:
Now that you know how to play this suit, remember NOT to split your honors with QJxx when you're on defense against a strong declarer.

It may take strong nerves, but your opponent should go up with the king if he knows the odds, and then you'll win two tricks in the suit instead of one.