The most common and most likely answer to this crossword clue is the 2 plus 6 letter word IN UNISON
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More clues leading to the result IN UNISON
- Agreeing with one sister: it’s found only intermittently
- Altogether in agreement
- With or without harmony
- One sister, one child — as one
- Together as part of a trade union
- Complete agreement could be shop steward’s position
- 27 All in one voice say “bliss at last in marriage!”
- Under cover head of staff interrupting marriage at once
- One sister and one kid, all together
- Together as public service union members?
Buddy explains!

The straight part
We know that "All in one voice say/age" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case all in one voice say/age = in unison.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.