Opening, n.
1. The act or process of opening; a beginning; commencement; first appearance; as, the opening of a speech. The opening of your glory was like that of light. Dryden.
2. A place which is open; a breach; an aperture; a gap; cleft, or hole. We saw him at the opening of his tent. Shak.
3. Hence: A vacant place; an opportunity; as, an opening for business. [Colloq.] Dickens.
4. A thinly wooded space, without undergrowth, in the midst of a forest; as, oak openings. [U.S.] Cooper.
Shades of meaning
Fernald has no entry of its own for opening; he lists it under beginning, entrance.
He lists it without comment; the entries above explain its neighbors.