Setting up partner's slow winner

En route to a 88% game in an online individual tournament, I pick up this hand and partner does well to not compete to 2S:

I start off with a lead of 8S.  Partner cashes her two top spades and leads back a small diamond to my Ace of diamonds. I cash the Queen of Spades.  Partner discards the 8 of diamonds.

What should you lead next?

Without thinking about it, I lead back a diamond and now, it was too late. Declarer was able to get out for down 1.

There is no diamond ruff to be had. If partner had had a doubleton, she would (should) have led the 8 of diamonds and discarded the 6 of diamonds under the Queen.  So, partner and declarer both have only diamond each. If declarer has 6 hearts and 2 clubs, there is nothing to be done. But if partner has a slow club winner, it is now or never.  Dummy's diamond winners are not cashing unless declarer can pull trumps.  So, I should lead a club now to set up partner's Queen of clubs.  When declarer takes the losing finesse, I should lead a second club.

On the actual layout, this also has the nice side-effect of taking out declarer's entries to the good diamonds while partner retains a trump.  Partner then gets one more trick with her queen of clubs.