Initially you only have one winner so you will need to find 3 more and the bidding suggests partner doesn't have a lot either BUT don't despair. Maybe partner has Diamond Ace and you could get a ruff. Maybe partner has control of the trump suit and you might get a ruff after one round??

So let's lead our singleton Diamond and see what happens.

Partner wins first trick and plays back the ♦9. What does that mean? Oh he wants me to play a Spade back - maybe he has King or singleton. So without much ado you play Ace and another spade and get lovely surprise when partner ruffs. You have taken the first 4 tricks and declarer has gone off. Any other defence and declarer gets home losing just one trick in each suit except trumps.

You can also play out the following hand  to see how the hand pans out.    (You need bridgvu.exe programme  and it is available free from   http://www.haroldschogger.com/movies.html )