The most common and most likely answer to this crossword clue is the 7 letter word TSUNAMI
I've seen this crossword clue in The Times
T
S
U
N
A
M
I
More clues leading to the result TSUNAMI
- Threat from deep from one football team, way back
- Giant wave — in it chap in front of us gets swept over
- Big wave from bloke returning in new suit
- Wave initially to Sophie, a friend in Paris
- Wave degree student group in IT returned
- Seen in midnight sun, a mighty big wave
- Am I nuts swimming in this? Yes
- Wave from our setter on time to meet French friend
- Yorkshire newspaper writer’s article about cause of flooding
- By 2 am, second terrible natural disaster
Buddy explains!

The straight part
We know that "Wave" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case wave = tsunami.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 TSUNAMI mean?
TSUNAMI noun- A very large and destructive wave, generally caused by a tremendous disturbance in the ocean, such as an undersea earthquake or volcanic eruption. Tsunami are usually a series of waves, or wave train.
- A large and generally unstoppable surge.