The most common and most likely answer to this crossword clue is the 5 plus 4 letter word OZONE HOLE
O
Z
O
N
E
H
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E
More clues leading to the result OZONE HOLE
- A stratospherically bad environmental issue?
- Australian pit contains single air gap
- Individual in Australia reported complete environmental concern
- Has a debt for personal total to auditor? It increases hazardous burn rate
- Australia — One spot where this protective top cover is missing
- Old region entirely without source of increased UV rays
Buddy explains!

The straight part
We know that "air gap" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case air gap = ozone hole.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.