The most common and most likely answer to this crossword clue is the 4 letter word OKTA
O
K
T
A
More clues leading to the result OKTA
Buddy explains!
The straight part
We know that "amount of obscured sky" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case amount of obscured sky = okta.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 OKTA mean?
OKTA noun- One eighth of the total area of the celestial dome; used as a measure of cloudiness (one okta means that one eighth of the sky is obscured, two oktas that one quarter is obscured, and so on).