Combine the water, sugar and ginger in a small sauce pan and bring to a boil.  Simmer for 5 minutes to dissolve the sugar and infuse the flavor of the ginger.

Remove from the heat and strain the ginger out.  Allow the syrup to cool (you can use an ice water bath to speed this up, just put the sauce pot in a big bowl of ice water and stir occasionally).

In the blender, comine the cool syrup, cilantro and the juice of 1 lime.  Blend on high until smooth.  At  this point you can use a fine mesh seive to strain out any solids that remain, but it's not terribly necessary.

In a cocktail shaker with some ice, combine the Tequila, cilantro syrup, lime and clementine juice. 

Using a lime wedge, moisten the rims of your martini glass.  Dunk the glass in some kosher salt.

Shake up the cocktail and strain it into the salted martini glass, garnish with a wheel of clementine.