The most common and most likely answer to this crossword clue is the 8 letter word BETRAYAL
I've seen this crossword clue in Financial Times
B
E
T
R
A
Y
A
L
More clues leading to the result BETRAYAL
- British fish and others around for shopping
- Risk money, a pound, after some light shopping?
- Barely treasonous at first, a criminal act that’s treasonous!
- Double-dealing drug carrier’s caught in abandoned lab
- Sell-out show unintentionally disheartened everybody
- Choice fish almost completely selling out
- Disloyalty in university mostly after letter about resistance
- Opinion shown by two men is breach of trust
- Old carrier left to absorb another one in bad faith
- Speculation before man left after a deception
Buddy explains!

The straight part
We know that "Double-dealing" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case double-dealing = betrayal.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 BETRAYAL mean?
BETRAYAL noun- The act of betraying