The most common and most likely answer to this crossword clue is the 6 letter word HEUGHS
H
E
U
G
H
S
Buddy explains!
The straight part
We know that "the Scottish valleys" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case the scottish valleys = heughs.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 HEUGHS mean?
HEUGHS noun- A steep crag or cliff, especially one with overhanging sides
- A glen with steep, overhanging sides
- A steep excavation, especially a coal pit