The most common and most likely answer to this crossword clue is the 8 letter word AQUARIUS
I've seen this crossword clue in The Guardian
A
Q
U
A
R
I
U
S
More clues leading to the result AQUARIUS
- Sign at first and quibble, usually afterwards, when hybrid car doesn’t start
- Adult, one after two pints briefly confronting American stars
- Song from Hair stars
- A sign of where swimmers are finally getting changed
- Fish tanks losing large number is one of the signs of winter
- Sign given by a queen, a king, and one leading American
- An age that dawned for Waterman?
- Quasar exploding round one high-class constellation
- One taking on water, was square rig just out of trim?
- Sign of a heretic skirting round question
Buddy explains!
The straight part
We know that "Sign" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sign = aquarius.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.