When construed with certain prepositions the verb assumes senses which it has with the cognate adverbs. to let into: (a) to admit to, give…

transitive. To introduce; to precede (something) as an introduction; to come before or in front of.

intransitive. To make introductory or prefatory remarks; to write or speak a preface. Obsolete.

transitive. To precede as a prelude or preliminary action; to serve as a prelude to; to prepare the way for, introduce, foreshadow.

To usher in (a time, action, matter, etc.); to bring forward with preliminary or preparatory matter; to start, open, begin.

transitive. To make a preamble or preliminary to; to preface. Also figurative.