For general confusion:
* Clarify
* Explain
* Enlighten
* Elucidate
* Understand
* Comprehend
For confusion caused by misleading information:
* Truth
* Accuracy
* Clarity
* Certainty
For confusion caused by emotional distress:
* Calm
* Tranquility
* Peace
* Composure
For confusion caused by a lack of knowledge:
* Knowledge
* Understanding
* Awareness
* Education
The best antonym for "confuse" will depend on the specific situation and the intended meaning.