The most common and most likely answer to this crossword clue is the 9 letter word PROCESSES
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More clues leading to the result PROCESSES
Buddy explains!

The straight part
We know that "Trials" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case trials = processes.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 PROCESSES mean?
PROCESSES noun- A series of events which produce a result (the product).
- A set of procedures used to produce a product, most commonly in the food and chemical industries.
- A path of succession of states through which a system passes.
- Successive physiological responses to keep or restore health.
- Documents issued by a court in the course of a lawsuit or action at law, such as a summons, mandate, or writ.
- An outgrowth of tissue or cell.
- A structure that arises above a surface.
- An executable task or program.
- The centre mark that players aim at in the game of squails.
- To perform a particular process on a thing.
- To retrieve, store, classify, manipulate, transmit etc. (data, signals, etc.), especially using computer techniques.
- To think about a piece of information, or a concept, in order to assimilate it, and perhaps accept it in a modified state.
- To develop photographic film.
- To take legal proceedings against.
- To walk in a procession