The most common and most likely answer to this crossword clue is the 6 letter word FORUMS
F
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M
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Buddy explains!
The straight part
We know that "Discussion groups" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case discussion groups = forums.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 FORUMS mean?
FORUMS noun- A place for discussion.
- A gathering for the purpose of discussion.
- A form of discussion involving a panel of presenters and often participation by members of the audience.
- An Internet message board where users can post messages regarding one or more topics of discussion.
- A square or marketplace in a Roman town, used for public business and commerce.