The most common and most likely answer to this crossword clue is the 9 letter word HAILSTORM
I've seen this crossword clue in The Times
H
A
I
L
S
T
O
R
M
More clues leading to the result HAILSTORM
- Terrible weather greets Mike behind rocky peak
- Greetings to Royal Marines in spell of bad weather
- Greetings to Royal Marines – violent shower?
- Morals hit badly when Sky drops The Stones?
- After heroin, moralist turns to a drop of the hard stuff
- Addresses leading to jolly unpleasant shower
- Welcome attack in shower of pellets
Buddy explains!

The straight part
We know that "shower of pellets" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case shower of pellets = hailstorm.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 HAILSTORM mean?
HAILSTORM noun- A storm characterized by lots of large hail.