The most common and most likely answer to this crossword clue is the 6 letter word BOURSE
I've seen this crossword clue in Financial Times
B
O
U
R
S
E
Buddy explains!
The straight part
We know that "stock exchange" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case stock exchange = bourse.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 BOURSE mean?
BOURSE noun- A stock exchange.
- A meeting of stamp collectors and/or dealers, where stamps and covers are sold or exchanged.
- The swollen basal part of an inflorescence axis at the onset of fruit development; it bears leaves whose axillary buds differentiate and may grow out as shoots.