The most common and most likely answer to this crossword clue is the 6 letter word RIGOUR
I've seen this crossword clue in Financial Times
R
I
G
O
U
R
More clues leading to the result RIGOUR
- Harshness of regime is guarantee of unpopular rumbles initially
- Carefulness with which engineer approaches old Chaldean city
- Austerity in dress runs for short time
- Stiffness affected Igor – game’s upset
- Trying to hurry occasionally creates hardship
- Scaffolder reported stiffness
- Harshness voiced by fraudster?
- Trial cook lasting forty-five minutes?
- Hardship of ship worker reportedly
- Meticulousness of person working on ship being reported
Buddy explains!

The straight part
We know that "Trial" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case trial = rigour.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 RIGOUR mean?
RIGOUR noun- Severity or strictness.
- Harshness, as of climate.
- A trembling or shivering response.
- Character of being unyielding or inflexible.
- Shrewd questioning.
- Higher level of difficulty.