I've caught a few trout where the North Fork enters the reservoir, but it's pretty hit and miss since it also seems to be a popular swimming hole. Worms and spinners worked there. It's a nice spot to fish with the kids. Grass, not rocks, and protected from the wind.
Further up the river near Fish creek (I think) I landed a 21" steelhead on light trout tackle. That was by far the best fish fight I ever had. 4 pound test, and a tiny spinner I had been using to try and catch trout. I thought he was going to strip my reel a few times as he kept running down the river. I didn't mean to catch him, and wasn't allowed to keep him in any case so I let him go, but he fought well and deserved to spawn anyway
For me the problem with the Clack is access. Where I have been able to get to the river I have caught fish. Finding a spot along the bank where someone hasn't called dibs is tough on the weekend.