General clarity:
* Obviously
* Evidently
* Plainly
* Distinctly
* Unmistakably
* Explicitly
* Precisely
* Definitely
* Certainly
Emphasizing visual clarity:
* Visibly
* Perceptibly
* Noticeably
* Readily
Emphasizing intellectual clarity:
* Intelligibly
* Understandably
* Cogently
* Articulately
* Lucidly
* Coherently
Emphasizing a lack of ambiguity:
* Unequivocally
* Categorically
* Absolutely
* Positively
Other synonyms:
* Easily
* Simply
* Straightforwardly
* Openly
* Honestly
* Frankly
The best synonym to use will depend on the context of your sentence.