The most common and most likely answer to this crossword clue is the 8 letter word LEXICONS
I've seen this crossword clue in The Daily Telegraph
L
E
X
I
C
O
N
S
More clues leading to the result LEXICONS
Buddy explains!

The straight part
We know that "dictionaries" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case dictionaries = lexicons.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 LEXICONS mean?
LEXICONS noun- The vocabulary of a language.
- A dictionary that includes or focuses on lexemes.
- A dictionary of Classical Greek, Hebrew, Latin, or Aramaic.
- The lexicology of a programming language. (Usually called lexical structure.)
- Any dictionary.
- The vocabulary used by or known to an individual. (Also called lexical knowledge)
- A vocabulary specific to a certain subject.