Formal:
* Elucidate
* Explain
* Expound
* Illustrate
* Articulate
* Define
* Specify
* Enumerate
Informal:
* Explain
* Make clear
* Spell out
* Break down
* Put simply
* Reiterate
* Elaborate
* Go into detail
More specific:
* Amplify (to make something bigger or louder)
* Refine (to make something more precise)
* Simplify (to make something easier to understand)
* Resolve (to remove confusion or doubt)
The best word to use will depend on the specific situation. Consider what you want to emphasize and the tone you want to convey.