The most common and most likely answer to this crossword clue is the 9 letter word LEVIATHAN
I've seen this crossword clue in Independent
L
E
V
I
A
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A
N
More clues leading to the result LEVIATHAN
- Following line, I haven't managed to net a monster
- Beast terribly evil nearby losing tail
- He, valiant, destroyed monster
- Formidable liberal with energy very odd in a hat
- Massive thing lit a haven development
- Travelling through time back to Jonah in poor whale
- Biblical monster?
- Ice hockey team overwhelmed by Alan, the Incredible Hulk
- Monster wants patriarch and prophet beheaded
- St Matthew’s almost within easy reach –- it’s huge!
Buddy explains!
The straight part
We know that "Formidable" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case formidable = leviathan.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 LEVIATHAN mean?
LEVIATHAN noun- A vast sea monster of tremendous strength, described as the most powerful and dangerous creature in the ocean.
- Something large; behemoth.
- Very large; gargantuan.