The most common and most likely answer to this crossword clue is the 8 letter word PIFFLING
I've seen this crossword clue in The Daily Telegraph
P
I
F
F
L
I
N
G
Buddy explains!
The straight part
We know that "trivial" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case trivial = piffling.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 PIFFLING mean?
PIFFLING verb- To act or speak in a futile, ineffective, or nonsensical manner.
- To waste, to fritter away.
- To be squeamish or delicate.
- Unimportant