The most common and most likely answer to this crossword clue is the 8 letter word JABBERED
I've seen this crossword clue in Financial Times
J
A
B
B
E
R
E
D
Buddy explains!
The straight part
We know that "Talked incoherently" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case talked incoherently = jabbered.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 JABBERED mean?
JABBERED verb- To talk rapidly, indistinctly, or unintelligibly; to utter gibberish or nonsense.
- To utter rapidly or indistinctly; to gabble.