The most common and most likely answer to this crossword clue is the 7 letter word WEBINAR
I've seen this crossword clue in The Guardian
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More clues leading to the result WEBINAR
Buddy explains!

The straight part
We know that "discussion online" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case discussion online = webinar.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 WEBINAR mean?
WEBINAR noun- An interactive seminar conducted via Internet. Usually a live presentation, lecture or workshop that happens in real time, as users participate through text-based chat, voice, video, or file-sharing.