The most common and most likely answer to this crossword clue is the 8 letter word SEASONED
I've seen this crossword clue in The Guardian
S
E
A
S
O
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D
More clues leading to the result SEASONED
- Among children, a boy is mature
- Veteran comatose as one drags chains in
- Veteran livened up
- Experienced unease as one dismantled fences
- Main issue journalist spiced up
- John and Jane finally tuck into surf & turf with salt and pepper
- Mature children embracing adult with child
- Experienced soprano helped to carry Oberon’s wings
- Experienced deaconess caught out surprisingly
- Mature offspring harbour an issue
Buddy explains!

The straight part
We know that "Mature" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case mature = seasoned.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 SEASONED mean?
SEASONED verb- To make fit for any use by time or habit; to habituate; to accustom; to inure.
- (by extension) To prepare by drying or hardening, or removal of natural juices.
- To become mature; to grow fit for use; to become adapted to a climate.
- To become dry and hard, by the escape of the natural juices, or by being penetrated with other substance.
- To mingle: to moderate, temper, or qualify by admixture.
- To copulate with; to impregnate.
- To flavour food with spices, herbs or salt.
- Experienced, especially in terms of a profession or a hobby
- Of a food, often a liquid: containing seasonings