The most common and most likely answer to this crossword clue is the 9 letter word WORKBOOKS
I've seen this crossword clue in Independent
W
O
R
K
B
O
O
K
S
Buddy explains!

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 WORKBOOKS mean?
WORKBOOKS noun- A book, used by a student, in which answers and workings may be entered besides questions and exercises.
- A book, used by a business, containing a record of work to be done, or work completed.
- A collection of spreadsheets stored in the same file.