The most common and most likely answer to this crossword clue is the 6 letter word MAXIMS
I've seen this crossword clue in Independent
M
A
X
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M
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Buddy explains!

The straight part
We know that "gnomes" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case gnomes = maxims.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 MAXIMS mean?
MAXIMS noun- A self-evident axiom or premise; a pithy expression of a general principle or rule.
- A precept; a succinct statement or observation of a rule of conduct or moral teaching.