The most common and most likely answer to this crossword clue is the 7 letter word YOUNGER
I've seen this crossword clue in The Daily Telegraph
Y
O
U
N
G
E
R
More clues leading to the result YOUNGER
- Less mature, the solver's stifling snigger occasionally?
- Junior tearaway, ultimately having no urge to reform
- Less mature guy, one off on run
- Say name backward, restricted by one’s being less mature
- New guy, Nero, is not so old
- We all were yesterday!
- Comparatively raw solver, no good with Elgar, disheartened
- More inexperienced guy, one out before end of over
- Not so old, one guy adrift on river
- Almost one year gone, you eventually becoming no ____
Buddy explains!

The straight part
We know that "More inexperienced" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case more inexperienced = younger.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 YOUNGER mean?
YOUNGER adjective- In the early part of growth or life; born not long ago.
- At an early stage of existence or development; having recently come into existence.
- (Not) advanced in age; (far towards or) at a specified stage of existence or age.
- Junior (of two related people with the same name).
- (of a decade of life) Early.
- Youthful; having the look or qualities of a young person.
- Of or belonging to the early part of life.
- Having little experience; inexperienced; unpracticed; ignorant; weak.
- One who is younger than another.