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

For example, does this make sense grammatically? Assume I can’t remove the words, his statement.

He then specified his statement: ‘There will be no water involved. It’s a rocketship 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.