So far no luck with a death. We found the Partridges in a local cemetery but not Anne. We know a brother William passed in London, ON in February 1874 and no burial for him either even though he was a prominent member of the community according to his obit
I saw a few trees with the obit on Anc for William, but it's not the full artlcle. I just want to make sure you know there is much more to it, especially with William's involvement with "the old St Andrew's Church" in his old neighbourhood in London, and how involved prior Clark generations were involved with their church.
I'm thinking it might be worth your while tracking down this Church, and seeing if they have their own cemetery on the grounds. It would make sense that he, and perhaps his siblings would be buried there.
EDITAfter I posted above, I looked around for the Rev. of the above mentioned church, as he would be buried at the church if they indeed had a burial ground.
It turns out that during the time when your William was getting involved in St Andrews, the Rev William Proudfoot was there. When Proudfoot died, he was buried in the Proudfoot family cemetery which, at some point, became the Oakland/Proudfoot Cemetery, where the Partridge's are buried. So, all the Clark's are probably there, but, if you read about the cemetery here:
http://geneofun.on.ca/cems//ONMID12702 you will see that records were lost in a fire, and the cemetery had been badly neglected. Perhaps they are there, but the headstones damaged, or unreadable.
The index for the cemetery says they have taken pictures of all visible stones in the entire cemetery. Looking at the index, there are many that just can't be read, but there is a couple where they can make out "Anne".
On the day of William Clark's funeral, the same newspaper that ran the obit put an entry in that his remains were interred this day, and the funeral was largely attended. No mention of the where, just that he was interred.