The most common and most likely answer to this crossword clue is the 7 plus 2 plus 6 letter word SILENCE IS GOLDEN
I've seen this crossword clue in The Daily Telegraph
S
I
L
E
N
C
E
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S
G
O
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D
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N
More clues leading to the result SILENCE IS GOLDEN
- Appeal for quiet colleges is binned, failing to start, unfortunately
- Peace slogan in lodge, since lines altered
- Better not talk in lesson prepared with diligence
- Frolicking inside college in outskirts of Swindon? Best say nothing
- What good listeners know, lesson that’s gone over with diligence
- Ill-disposed view of din?
- Warning against rash talk from scold seeing line blurred?
- You may be silver-tongued but not speaking might help better
Buddy explains!
The straight part
We know that "Best say nothing" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case best say nothing = silence is golden.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.