The most common and most likely answer to this crossword clue is the 7 plus 2 letter word LETTING GO
I've seen this crossword clue in The Guardian
L
E
T
T
I
N
G
G
O
More clues leading to the result LETTING GO
Buddy explains!
The straight part
We know that "Dismissing someone/discussing the matter no further" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case dismissing someone/discussing the matter no further = letting go.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.