The most common and most likely answer to this crossword clue is the 8 letter word SYLLABLE
I've seen this crossword clue in The Guardian
S
Y
L
L
A
B
L
E
Buddy explains!
The straight part
We know that "One has one of them, another three" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one has one of them, another three = syllable.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 SYLLABLE mean?
SYLLABLE noun- A unit of human speech that is interpreted by the listener as a single sound, although syllables usually consist of one or more vowel sounds, either alone or combined with the sound of one or more consonants; a word consists of one or more syllables.
- The written representation of a given pronounced syllable.
- A small part of a sentence or discourse; anything concise or short; a particle.
- To utter in syllables.