How can I recreate the Clarity effect in Photoshop CS6?

The original "clarity" technique is just a Midtone contrast adjustment, the original idea as far as I know is from Mac Holbert formally of Nash Editions. Recipe is below but Mac used to have an action on his web site (I have it too and could send). Or build your own. Here's the steps:

Mac Holbert's Midtone Contrast 

1. Highlight your top layer in your Layers Palette then: 

2a. In CS I: Select Layer->New->Layer to create a new, blank layer at the top of your Layer Stack. Then, holding down 

your Opt Key (Mac) / Alt Key (PC), select Merge Visible from the fly-down menu on the right side of your Layers Palette. 

Be sure to keep the Opt/Alt depressed until you see the blank layer update. You should now have an additional layer at the 

top of your layer stack. It represents how the image would appear if you had flattened your layers. Rename this layer 

“Midtone Contrast” 

      -OR- 

2b. In CS II: Holding down your Opt Key (Mac) / Alt Key (PC), select Merge Visible from the fly-down menu on the right 

side of your Layers Palette. Be sure to keep the Opt / Alt depressed until you see the blank layer update. You should now 

have an additional layer at the top of your layer stack. It represents how the image would appear if you had flattened your 

layers. Rename this layer “Midtone Contrast” 

3. Next double-click on the Midtone Contrast layer icon to bring up the Layer Style Palette. Change the Blend Mode to 

Overlay and lower the Blend Mode Opacity to 20%. Now move the left “This Layer” slider to 70. Now Split away the left 

side of that slider by holding down the Opt / Alt key and move it to 50. Repeat the same process on the right “This Layer” 

slider, moving the sliders to 185 and 205 respectively. Then select “OK”. 

4. Now select Filter->Other->High Pass. In the High Pass Palette set the radius to 50 and select “OK”. Now select Image- 

>Adjustments->Desaturate. The Midtone Contrast layer is now complete. At 20% opacity it should be very subtle, but 

noticable. The effect can be decreased or increased by raising or lowering the Midtone Contrast Layer opacity. I’ve found 

that the proper setting can usually be found between 20% and 40% opacity. Above 40% one risks creating “halo” artifacts 

that are visually distracting.