The most common and most likely answer to this crossword clue is the 7 letter word BREATHE
I've seen this crossword clue in The Daily Telegraph
B
R
E
A
T
H
E
More clues leading to the result BREATHE
- Inspire soldiers to swim outside
- Inspire to live, concealing heart condition
- Gasp for a brew of herb tea
- Speak with quiet intensity about getting into swim
- Swim round about and respire
- Hear bet is off and get some air
- Bather, swimming, needs energy to do this?
- Herb tea’s brewed, take in the air
- Live round’s opening, puncturing strike explosive
- Sombre at heart stifling sigh
Buddy explains!

The straight part
We know that "take in the air" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case take in the air = breathe.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 BREATHE mean?
BREATHE verb- To draw air into (inhale), and expel air from (exhale), the lungs in order to extract oxygen and excrete waste gases.
- To take in needed gases and expel waste gases in a similar way.
- To inhale (a gas) to sustain life.
- To live.
- To draw something into the lungs.
- To expel air from the lungs, exhale.
- To exhale or expel (something) in the manner of breath.
- To give an impression of, to exude.
- To whisper quietly.
- To pass like breath; noiselessly or gently; to emanate; to blow gently.
- To exchange gases with the environment.
- To rest; to stop and catch one's breath.
- To stop, to give (a horse) an opportunity to catch its breath.
- To exercise; to tire by brisk exercise.
- To passionately devote much of one's life to (an activity, etc.).