The most common and most likely answer to this crossword clue is the 10 letter word ALTOCUMULI
A
L
T
O
C
U
M
U
L
I
Buddy explains!

The straight part
We know that "clouds" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case clouds = altocumuli.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 ALTOCUMULI mean?
ALTOCUMULI noun- A fleecy cloud formation consisting of large whitish or greyish globular cloudlets with shaded portions, often grouped in flocks or rows. (Abbreviated Ac.)