The most common and most likely answer to this crossword clue is the 11 letter word HYDROMETEOR
I've seen this crossword clue in The Times
H
Y
D
R
O
M
E
T
E
O
R
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The straight part
We know that "Weather that's wet" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case weather that's wet = hydrometeor.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 HYDROMETEOR mean?
HYDROMETEOR noun- Rain, snow and other precipitation products of the condensation of atmospheric water vapour