The most common and most likely answer to this crossword clue is the 9 letter word SLIGHTEST
I've seen this crossword clue in Financial Times
S
L
I
G
H
T
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T
More clues leading to the result SLIGHTEST
- Most insignificant languages ultimately easiest to pick up
- Most insignificant group sent up in insult
- What sounds like cunning experiment is most trivial
- Son least heavy, carrying least weight?
- Tiniest moan about large cricket match
- Most insignificant website regularly supporting insult
- Tricky exam to say the least?
- Most paltry content in Maxwell's light estimates
- Least tricky exam, reportedly
- Minimal show of relief about lawyer’s first trial
Buddy explains!

The straight part
We know that "most trivial" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case most trivial = slightest.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 SLIGHTEST mean?
SLIGHTEST verb- To treat as unimportant or not worthy of attention; to make light of.
- To give lesser weight or importance to.
- To treat with disdain or neglect, usually out of prejudice, hatred, or jealousy; to ignore disrespectfully.
- To act negligently or carelessly.
- (of a fortification) To render no longer defensible by full or partial demolition.
- To make even or level.
- To throw heedlessly.
- Small
- Of slender build
- Even, smooth or level
- (especially said of the swa) still; with little or no movement on the surface
- Foolish; silly; not intellectual.
- Bad, of poor quality.
- Slighting; treating with disdain.