The most common and most likely answer to this crossword clue is the 5 letter word OZONE
I've seen this crossword clue in The Times
O
Z
O
N
E
More clues leading to the result OZONE
- Gas from individual on the east side of Australia
- Australia has a certain invigorating air
- Australian individual, a gas!
- Fresh air round district is wanted
- Australian unit making gas
- A person going after Australian sea air
- Toxic gas round area
- Bracing air round region
- Australian figure in fresh air
- Sea air I discovered east of Australia
Buddy explains!

The straight part
We know that "Sea air" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sea air = ozone.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 OZONE mean?
OZONE noun- An allotrope of oxygen (symbol O₃) having three atoms in the molecule instead of the usual two; it is a blue gas, generated from oxygen by electrical discharge.
- Fresh air, especially that breathed at the seaside and smelling of seaweed.
- To treat with ozone.