The most common and most likely answer to this crossword clue is the 9 letter word WELL-WORN
I've seen this crossword clue in Financial Times
W
E
L
L
-
W
O
R
N
Buddy explains!
The straight part
We know that "Stock" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case stock = well-worn.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 WELL-WORN mean?
WELL-WORN adjective- Showing signs of wear because of extensive use
- (by extension) trite or hackneyed; repeated too often