The most common and most likely answer to this crossword clue is the 8 letter word DECLARER
I've seen this crossword clue in The Daily Telegraph
D
E
C
L
A
R
E
R
Buddy explains!
The straight part
We know that "one with something to say" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one with something to say = declarer.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 DECLARER mean?
DECLARER noun- The person who wins the bidding and so declares what suit will be trump.
- One who declares.
- A statement that declares the properties of a variable or contributes to doing so.