The most common and most likely answer to this crossword clue is the 8 plus 6 letter word CIRCULAR LETTER
I've seen this crossword clue in The Times
C
I
R
C
U
L
A
R
L
E
T
T
E
R
More clues leading to the result CIRCULAR LETTER
Buddy explains!
The straight part
We know that "O/means to disseminate information" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case o/means to disseminate information = circular letter.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.