The most common and most likely answer to this crossword clue is the 9 letter word PARTICLES
I've seen this crossword clue in The Guardian
P
A
R
T
I
C
L
E
S
More clues leading to the result PARTICLES
Buddy explains!
The straight part
We know that "very small ones" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case very small ones = particles.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 PARTICLES mean?
PARTICLES noun- A very small piece of matter, a fragment; especially, the smallest possible part of something.
- Any of various physical objects making up the constituent parts of an atom; an elementary particle or subatomic particle.
- A word that has a particular grammatical function but does not obviously belong to any particular part of speech, such as the word to in English infinitives or O as a vocative particle.
- A part of speech which cannot be inflected: an adverb, preposition, conjunction or interjection.
- In the Roman Catholic church, a crumb of consecrated bread; also the smaller breads used in the communion of the laity.