The most common and most likely answer to this crossword clue is the 8 letter word FIREBALL
I've seen this crossword clue in The Times
F
I
R
E
B
A
L
L
More clues leading to the result FIREBALL
- Energetic person in sack dance
- Dismiss dance as a transient flashy thing
- Live wire at the dance after excitement
- Loud anger over party album by Deep Purple
- Lively personās lapse into sin involving anger against bishop
- Devastating thing to dismiss everyone, with billion invested
- Live wire female's anger beginning to bother everybody
Buddy explains!

The straight part
We know that "a transient flashy thing" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a transient flashy thing = fireball.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 FIREBALL mean?
FIREBALL noun- A ball of fire, especially one associated with an explosion.
- A meteor bright enough to cast shadows.
- A class of sailing dinghy with a single trapeze and a symmetrical spinnaker, sailed by a crew of two.
- A charge made of a disc-shaped bomb shell, with four sets of flames, at the top, bottom and on either side.
- A ball filled with combustibles to be thrown among enemies.
- To explode in a ball of flame.
- To pitch the ball very fast.
- To attack with balls of fire.