The most common and most likely answer to this crossword clue is the 10 letter word TERMINATOR
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More clues leading to the result TERMINATOR
- Minor treat, fantastic series of sci-fi films
- Assassin's period in schedule brought up
- Film session with popular thespian dropping cocaine
- One ending spell governing country: one Conservative finally ousted
- One ending a period in a degenerate uprising
- He finishes off period at school in a history module
- One concluding art with no merit should be scrapped
- Traitor involved with men becomes killer
- Iron matter turned into cyborg
- He finishes off period in a reversal of twaddle
Buddy explains!

The straight part
We know that "One concluding" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one concluding = terminator.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 TERMINATOR mean?
TERMINATOR noun- Someone who terminates or ends something, especially (in later use) an assassin or exterminator.
- The line between the day side and the night side of a moon, planet or other celestial body.
- A DNA sequence which causes RNA transcription to cease and an mRNA transcript to break off.
- An electrical device that absorbs reflection at the end of a transmission line.
- An intelligent android created to destroy humans (after the 1984 film The Terminator).