The most common and most likely answer to this crossword clue is the 6 letter word DOUSED
I've seen this crossword clue in The Guardian
D
O
U
S
E
D
More clues leading to the result DOUSED
Buddy explains!

The straight part
We know that "flooded" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case flooded = doused.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 DOUSED mean?
DOUSED verb- To plunge suddenly into water; to duck; to immerse.
- To fall suddenly into water.
- To put out; to extinguish.
- To strike, beat, or thrash.
- To strike or lower in haste; to slacken suddenly