The most common and most likely answer to this crossword clue is the 10 letter word HAILSTORMS
I've seen this crossword clue in The Guardian
H
A
I
L
S
T
O
R
M
S
Buddy explains!

The straight part
We know that "Frozen waterfalls" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case frozen waterfalls = hailstorms.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 HAILSTORMS mean?
HAILSTORMS noun- A storm characterized by lots of large hail.