The most common and most likely answer to this crossword clue is the 3 plus 2 letter word END OF
I've seen this crossword clue in The Times
E
N
D
O
F
More clues leading to the result END OF
Buddy explains!
The straight part
We know that "that concludes the debate!" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case that concludes the debate! = end of.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.