The most common and most likely answer to this crossword clue is the 7 letter word LILTING
I've seen this crossword clue in The Times
L
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More clues leading to the result LILTING
Buddy explains!

The straight part
We know that "Jaunty" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case jaunty = lilting.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 LILTING mean?
LILTING verb- To do something rhythmically, with animation and quickness, usually of music.
- To sing cheerfully, especially in Gaelic.
- To utter with spirit, animation, or gaiety; to sing with spirit and liveliness.
- A type of lively singing without any musical accompaniment, where the tune itself is sung, often to nonsense syllables.
- Having a lilt; with energy, spirit and sprightliness; lively and cheerful.