The most common and most likely answer to this crossword clue is the 8 letter word SNOWFALL
I've seen this crossword clue in The Sunday Telegraph
S
N
O
W
F
A
L
L
More clues leading to the result SNOWFALL
Buddy explains!

The straight part
We know that "Form of precipitation" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case form of precipitation = snowfall.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 SNOWFALL mean?
SNOWFALL noun- An instance of falling of snow.
- The amount of snow that falls on one occasion.