The most common and most likely answer to this crossword clue is the 7 letter word GLACIER
I've seen this crossword clue in The Daily Telegraph
G
L
A
C
I
E
R
More clues leading to the result GLACIER
- Around Channel Islands, large unwieldy mass of ice
- First to grow more delicate Alpine flower?
- Icy formation finally becoming more intricate
- Mostly large ice moving?
- More fancy following golf? It’s long and really slow-moving!
- Coin oddly found in unusually large white flower?
- Grand to start with, then more ruffled, one goes slowly downhill
- Frozen mass that’s large, ice endlessly shifting
- Large ice formation? Not quite, out East
- Alpine flower
Buddy explains!

The straight part
We know that "Large ice formation" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case large ice formation = glacier.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 GLACIER mean?
GLACIER noun- A large body of ice which flows under its own mass, usually downhill.