The most common and most likely answer to this crossword clue is the 6 letter word CAIRNS
I've seen this crossword clue in The Daily Telegraph
C
A
I
R
N
S
More clues leading to the result CAIRNS
Buddy explains!
The straight part
We know that "Constructions assembled in rough natural stone" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case constructions assembled in rough natural stone = cairns.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 CAIRNS mean?
CAIRNS noun- A rounded or conical heap of stones erected by early inhabitants of the British Isles, apparently as a sepulchral monument.
- A pile of stones heaped up as a landmark, to guide travelers on land or at sea, or to arrest attention, as in surveying, or in leaving traces of an exploring party, etc.
- A cairn terrier.