The most common and most likely answer to this crossword clue is the 3 letter word YEA
I've seen this crossword clue in Financial Times
Y
E
A
More clues leading to the result YEA
- Definitely a period of nine months?
- Vote for period to be reduced
- You will get a positive response
- Vote for shortened annual period
- Affirmation among many earlier
- Originally, your elderly aunt says yes
- Positive vote getting rid of extremists very early
- “The Essence of Honey-eating” indeed!
- Vote for one revolution without end
Buddy explains!

The straight part
We know that "Affirmation" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case affirmation = yea.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 YEA mean?
YEA noun- An affirmative vote, usually but not always spoken
- Yes.
- Thus, so (now often accompanied by a hand gesture).
- Or even, or more like, nay. Introduces a stronger and more appropriate expression than the preceding one.
- (in some dialects of American English, including Southern, Western, and African American Vernacular) Yeah, right, yes.
- Expressing joy, celebration, glee, etc.