The most common and most likely answer to this crossword clue is the 3 plus 6 letter word RED MULLET
I've seen this crossword clue in Financial Times
R
E
D
M
U
L
L
E
T
More clues leading to the result RED MULLET
- Swimmer studied, missing a certain style
- Swimmer’s revolutionary hairstyle
- Communist with once-trendy hairstyle? That's fishy
- Swimmer embarrassed by hairstyle
- Swimmer’s possibly East German hairdo
- Fish bloody, old cut
- Swimmer reveals what Ziggy Stardust had?
- Deter swimming around island for one particular swimmer
- Radical hairstyle for swimmer?
- School member’s ginger hairstyle
Buddy explains!
The straight part
We know that "One looking green about the gills? Quite the opposite" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one looking green about the gills? quite the opposite = red mullet.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.