Granola - how to reduce sugar
One good method that can help you get solid  results is grinding some of the oats in your recipe into oat flour.

Grinding the oats allows the starches in the oats to absorb liquids, which then swell and solidify when baked. This is the same way that all cookies and the like get their solidity, by starches that set.

My suggestion is to take a portion of the oats that you are using in the recipe and grind it in the food processor until it resembles coarse flour. After mixing together your wet ingredients (oil, sugar, honey), add  the oat flour and mix well before adding in your inclusions (whole oats, nuts, dried fruit, etc).

In addition, don't stir during baking, as this will allow the clusters to form better.

I personally make granola bars with this method, and they come out quite good.