The most common and most likely answer to this crossword clue is the 7 letter word LOURING
I've seen this crossword clue in The Guardian
L
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Buddy explains!

The straight part
We know that "Scowling" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case scowling = louring.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 LOURING mean?
LOURING verb- To frown; to look sullen.
- To be dark, gloomy, and threatening, as clouds; of the sky: to be covered with dark and threatening clouds; to show threatening signs of approach, as a tempest.
- The act of one who, or that which, lours.