The most common and most likely answer to this crossword clue is the 7 letter word ORIFICE
I've seen this crossword clue in Financial Times
O
R
I
F
I
C
E
More clues leading to the result ORIFICE
- Oregon provided diamonds for opening
- Opening for Irishman initially involved with diamonds
- Opening gold reserve, inserting single key
- Opening gold reserve, holding one key
- Opening hole on first round provided water — that’s hard
- Opening scripture lesson in workplace after first fellow’s gone
- Opening office with fellow going for scripture
- Opening old cereal that’s out of condition
- Providing gold and diamond rings in opening
- Crack troops provided rocks
Buddy explains!

The straight part
We know that "Opening" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case opening = orifice.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does ORIFICE mean?
ORIFICE noun- A mouth or aperture, such as of a tube, pipe, etc.; an opening.