The most common and most likely answer to this crossword clue is the 8 letter word UNIFYING
I've seen this crossword clue in Financial Times
U
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I
F
Y
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Buddy explains!
The straight part
We know that "It’s making one" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case it’s making one = unifying.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 UNIFYING mean?
UNIFYING verb- Cause to become one; make into a unit; consolidate; merge; combine.
- Become one.
- Unification
- Tending to unify; promoting unity; uniting.