The most common and most likely answer to this crossword clue is the 6 letter word LEADEN
I've seen this crossword clue in Financial Times
L
E
A
D
E
N
More clues leading to the result LEADEN
- Field study is dreary
- Gloomy field retreat
- Dull field study
- Dull study beginning with articles in French and English
- Depressing end of tale in Loaded
- Dull London market with no room for meetings
- Dull start, and little energy before conclusion of competition
- Cloudy ale had men scratching heads
- Heavy metal measurement
- Heavy head when half-cut (6
Buddy explains!

The straight part
We know that "Cloudy" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case cloudy = leaden.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 LEADEN mean?
LEADEN verb- To make or become dull or overcast.
- Made of lead.
- Pertaining to or resembling lead; grey, heavy, sluggish.
- Dull; darkened with overcast.