The most common and most likely answer to this crossword clue is the 6 letter word JUNIOR
I've seen this crossword clue in Independent
J
U
N
I
O
R
More clues leading to the result JUNIOR
- Youngster last to turn into journalist
- For end of month one ranks KS2 kid
- Lad has M with couturier losing face
- Sort of school French king goes up to after short month
- Pupil in short summer period starts to impress other residents
- Younger panel member heartlessly besieges Northern Ireland
- Every other journo in ours is inexperienced
- Third-year student's month in Spain before mid-April
Buddy explains!

The straight part
We know that "KS2 kid" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case ks2 kid = junior.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 JUNIOR mean?
JUNIOR noun- A younger person.
- A name suffix used after a son's name when his father has the same name (abbreviations: Jnr., Jr., Jun.).
- A third-year student at a high school or university.
- A junior barrister.
- Low in rank; having a subordinate role, job, or situation.
- (often preceded by a possessive adjective or a possessive form of a noun) Younger.
- Belonging to a younger person, or an earlier time of life.
- Of or pertaining to a third academic year in a four-year high school (eleventh grade) or university.