«فهو أن يكون معنى اللفظ ظاهراً لكنه يحتمل غيره، فيبين المراد بما هو الظاهر»
The word already has an apparent meaning but still admits another possibility; the speaker then confirms that the apparent meaning is intended.
This is bayan al-taqrir, confirmation. It introduces no entirely new meaning. Instead, it secures the meaning that was already predominant and restricts an alternative possibility.
Before the further wording, the apparent sense was available but not free of competing interpretations. After the confirmation, the same sense is established more firmly. This differs from tafsir of an ambiguous term, where the principal difficulty is that the intended object is not yet disclosed.