*Specify* is the best I can think of, but it doesn’t by itself 
capture the change from ambiguity to less ambiguity.

For example:
> "I spent my entire net worth to ride a ship", said Blake.
>
> "Since when did boats become so expensive?"
>
> Blake realized that he had been misunderstood, so he specified his statement. "It wasn't a boat. It was a *rocket*ship that I paid exorbitant amounts of money to ride."

I’ve tried searching for synonyms of *specify* and *clarify*, but
none of them does the trick.

A compound word or phrase would be acceptable.