The most common and most likely answer to this crossword clue is the 9 letter word BARRACUDA
I've seen this crossword clue in Independent
B
A
R
R
A
C
U
D
A
More clues leading to the result BARRACUDA
- Marine hunter's shortly to garrison displaced occupants of quads
- Radar Cuba developed for predatory type
- Cuban radar at sea missing navy’s fearsome swimmer
- It’s brought back to eat with a fish
- Save artist given partially digested food, a fish
- Almost jeer oddly undead voracious creature
- A big fish seen with copper and lawyer on Scottish island
- Bar artist consuming a small piece of tobacco and fish
- Hunting fish could pay regularly on Hebridean island
- Prevent artist, copper and district attorney getting fish
Buddy explains!

The straight part
We know that "fearsome swimmer" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fearsome swimmer = barracuda.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 BARRACUDA mean?
BARRACUDA noun- Any large marine fish of the genus Sphyraena that have elongated bodies, a projecting lower jaw, displaying prominent fang-shaped teeth, and are aggressive predators.
- One who uses harsh or predatory means to compete.