The most common and most likely answer to this crossword clue is the 7 letter word PUERILE
I've seen this crossword clue in The Sunday Telegraph
P
U
E
R
I
L
E
More clues leading to the result PUERILE
- Immature, undefiled island, we hear
- Said you must be in danger with drug, lacking maturity
- Rule I violated during exercise is trifling
- Unadulterated passage read out? That’s just childish
- Composed lie, pure and simple
- Silly posh royalty occupying stately home
- Immature anger following exertions around university
- Childish peril breaks broken European Union
Buddy explains!
The straight part
We know that "lacking maturity" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case lacking maturity = puerile.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 PUERILE mean?
PUERILE adjective- Childish; trifling; silly.
- Characteristic of, or pertaining to, a boy or boys; compare puellile.