The most common and most likely answer to this crossword clue is the 9 letter word CHECKLIST
I've seen this crossword clue in The Times
C
H
E
C
K
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T
More clues leading to the result CHECKLIST
- Reminder of reported nickname of Prague piano virtuoso?
- Reminder, itemised bill has tip added
- Be inclined to follow slow sort of schedule
- European composer’s audible reminder
- One likely ticked off by co-pilots?
- European composer, in recital, has things to do
- European composer uttered ‘things to do’?
- What’s used to verify threat to King going over border
Buddy explains!

The straight part
We know that "Reminder, itemised" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case reminder, itemised = checklist.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 CHECKLIST mean?
CHECKLIST noun- A list of tasks to be completed, names to be consulted, conditions to be verified and similar.
- An inventory, especially of species.