The most common and most likely answer to this crossword clue is the 9 letter word TITCHIEST
I've seen this crossword clue in Financial Times
T
I
T
C
H
I
E
S
T
Buddy explains!
The straight part
We know that "smaller than all the others" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case smaller than all the others = titchiest.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 TITCHIEST mean?
TITCHIEST adjective- Tiny, very small.
- Touchy, irritated.