Tennis court is on the way to Les Gets from the top of Pleney. Follow the fire road, where it drops into the double track on the right (rather than the savage steep road climb). It pops out on the road, which you cross & follow down into Les Gets.
As you get to the point where it’s just about on the road, you will see a tall grassy area on the right, probably with a flattened trail into the undergrowth. That’s TC.
There is actually a couple of trails there now. They pop out right at the top of the road back down to Morzine from LG.
Worth noting on the aforementioned double track (and just before) you will see a load of trails peeling off the side of the hill to the right. If you’re feeling brave, and it’s been dry, go explore 🙂