The most common and most likely answer to this crossword clue is the 13 letter word DISINTERESTED
I've seen this crossword clue in The Daily Telegraph
D
I
S
I
N
T
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R
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D
More clues leading to the result DISINTERESTED
- Dig up established edition, having no personal stake
- Fair-minded democrat beaten up in side street
- Detest insider falsely posing as impartial
- Objective lacking curiosity?
- Unearth established journalist that’s impartial
- Desire – it tends to dissipate if one’s impartial
- Objective is not accruing money at bank?
- Just unconcerned
- Dig up seed scattered around end of plot that’s detached
- Dessert in diet unusually generous
Buddy explains!

The straight part
We know that "Just/unconcerned" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case just/unconcerned = disinterested.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 DISINTERESTED mean?
DISINTERESTED adjective- Having no stake or interest in the outcome; free of bias, impartial.
- Uninterested, lacking interest.