The most common and most likely answer to this crossword clue is the 9 letter word MERCURIAL
I've seen this crossword clue in The Guardian
M
E
R
C
U
R
I
A
L
More clues leading to the result MERCURIAL
- Constant in aim, ruler not normally unpredictable
- Brilliant car bishop nicked from funeral
- In a kind of miracle, they say you are fickle
- Capricious magician dropping in to entertain court
- Temperamental car you and Den turned over
- Spymaster with cruel air, terribly volatile
- Moody scientist restricted in experimental realm
- Reclaim ground outside city that used to be unstable
- Attitude, when surrounded by wealthis to turn volatile
- Lively blackbird circling court
Buddy explains!
The straight part
We know that "fickle" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fickle = mercurial.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 MERCURIAL mean?
MERCURIAL noun- Any of the plants known as mercury, especially the annual mercury or French mercury (Mercurialis annua).
- A person born under the influence of the planet Mercury; hence, a person having an animated, lively, quick-witted or volatile character.
- A chemical compound containing mercury.
- A preparation of mercury, especially as a treatment for syphilis.
- Having a lively or volatile character; animated, changeable, quick-witted.
- Pertaining to the astrological influence of the planet Mercury; having the characteristics of a person under such influence (see adjective sense 1).
- Pertaining to the planet Mercury.
- Of or pertaining to the element mercury or quicksilver; containing mercury.
- Caused by the action of mercury or a mercury compound.
- Pertaining to Mercury, the Roman god of, among other things, commerce, financial gain, communication, and thieves and trickery; hence , money-making; crafty.