The most common and most likely answer to this crossword clue is the 6 letter word STERIC
S
T
E
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C
Buddy explains!
The straight part
We know that "Concerned with layout of tiny things" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case concerned with layout of tiny things = steric.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 STERIC mean?
STERIC adjective- Relating to or involving the arrangement of atoms in space.
- Of the repulsion of atoms due to closeness or arrangement