The most common and most likely answer to this crossword clue is the 4 plus 5 letter word KING PRAWN
I've seen this crossword clue in Independent
K
I
N
G
P
R
A
W
N
More clues leading to the result KING PRAWN
- Two chessmen, one of which captures a third
- Two men consuming tail of lobster and other crustacean
- Rook pinned in by two other pieces—that’s fishy
- Food found by two men on board round back of larder
- Seafood recipe initially welcomed by couple on board
- a Family doctor hurried outside with Pacific resident
Buddy explains!
The straight part
We know that "that’s fishy" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case that’s fishy = king prawn.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.