opencl.dll
This file is not a system component: your graphics driver. Restore it from the source that installed it rather than downloading a replacement.
Do not download this DLL on its own
Searching for a missing DLL by name leads to sites that hand you that single file. It is one of the oldest and most effective malware delivery methods there is, and a system DLL from an unknown source is indistinguishable from a deliberately modified one. There is never a legitimate reason to obtain a runtime component that way.
What it is
The OpenCL runtime, which lets software run compute work on the graphics card. It is installed by the GPU driver rather than by Windows or any redistributable.
Where you see it: Video editors, rendering software and anything doing GPU-accelerated computation.
The fix is to reinstall or update the graphics driver from NVIDIA, AMD or Intel, whichever applies. On systems with both integrated and discrete graphics, installing the driver for the integrated GPU as well often resolves it. Downloading an OpenCL.dll achieves nothing, because the library has to match the driver that implements it.
Why there is nothing to download here
There is no verified download we can offer for this one, because installing a file is not the fix. The steps above are what actually resolves it. That distinction matters: the sites ranking for this file name are selling a download that would not have helped even if it were safe.