The most common and most likely answer to this crossword clue is the 9 letter word OSCILLATE
I've seen this crossword clue in The Daily Telegraph
O
S
C
I
L
L
A
T
E
More clues leading to the result OSCILLATE
- Outstanding Liverpudlian singer primarily tackling early swing
- Black, maybe, note, after very big swing
- Let social maverick swing both ways
- What swinger will do in local site naughtily
- Be undecided about transformation in Tesla coil
- It’s a cello playing swing
- Swing singer featuring in bill — neither top nor bottom
- Show indecision seeing redevelopment of local site
- Swing, like songstress during old set revitalised
- First one caught in window support had to swing
Buddy explains!

The straight part
We know that "swing" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case swing = oscillate.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 OSCILLATE mean?
OSCILLATE verb- To swing back and forth, especially if with a regular rhythm.
- To vacillate between conflicting opinions, etc.
- To vary above and below a mean value.