The most common and most likely answer to this crossword clue is the 12 letter word MARSEILLAISE
I've seen this crossword clue in Financial Times
M
A
R
S
E
I
L
L
A
I
S
E
More clues leading to the result MARSEILLAISE
- Air, extremely assertive, M Lisle’s composed
- Unease about extremely reckless story raised in song
- Only the French would stand for it
- Horse friends brought up is featured in country air?
- The French marche militaire?
- Real smile as I run around in country air
- Nice country song from Israel – a smile breaks out
Buddy explains!
The straight part
We know that "song" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case song = marseillaise.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.