। ॥ ३१ ॥
In plain words
And when another means of knowledge blocks the primary meaning so that it cannot be taken, and the word goes instead to what the primary meaning is never found apart from — that going is called lakṣaṇā, implication.
Close to the Sanskrit
And when, from obstruction by another means of knowledge, there is non-acceptance of the primary meaning, the word's operation upon that which is not without the primary meaning is called lakṣaṇā.