One of the features available in Lightroom CC 2015.x that’s not available with Lightroom 6.x is the Dehaze tool. I’m not sure what magical coding is going on behind the curtain, but if it’s possible to duplicate this effect using the other sliders, it’s neither inherently obvious (at least to me) nor easy to do so. If you have a Lr CC subscription, updating to the latest version should give you access to the Dehaze tool. If you’re using a standalone version of Lr 6, all is not lost – thanks to Stu over at Prolost.com – as he’s made a series of presets available for download. You can buy the Dehaze presets as part of a larger preset package here, or you can download only the Dehaze presets for free (or by donation) here.
If you have Lr CC2015.1 or later the Dehaze slider will be under the Effects panel in the Develop module (below Grain). It’s also available as a slider with the mask tools (Graduated Filter, Radial Filter, etc). If you’re using Lr 6.1 or later, using Dehaze will only be possible using the downloaded presets mentioned above. As such, one of the limitations is that the presets are in graduations of 10 – i.e. one can add 50 or 60, but not 53 the way one could set the slider in Lr CC.