The most common and most likely answer to this crossword clue is the 7 letter word ICEFALL
I
C
E
F
A
L
L
More clues leading to the result ICEFALL
Buddy explains!

The straight part
We know that "adverse weather" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case adverse weather = icefall.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 ICEFALL mean?
ICEFALL noun- A relatively rapid and turbulent flow of ice, somewhat analogous to a waterfall.