The most common and most likely answer to this crossword clue is the 10 letter word PERORATION
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More clues leading to the result PERORATION
Buddy explains!

The straight part
We know that "closing remarks" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case closing remarks = peroration.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 PERORATION mean?
PERORATION noun- The concluding section of a discourse, either written or oral, in which the orator or writer sums up and commends his topic to his audience, particularly as used in the technical sense of a component of ancient Roman oratorical delivery.
- A discourse or rhetorical argument in general.