The most common and most likely answer to this crossword clue is the 4 plus 5 letter word MILK TOOTH
I've seen this crossword clue in The Times
M
I
L
K
T
O
O
T
H
Buddy explains!
The straight part
We know that "something cut at an early stage" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case something cut at an early stage = milk tooth.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 MILK TOOTH mean?
MILK TOOTH noun- Any tooth of the first set of teeth of young people (or livestock).