Solution for 22 September cryptic crossword clue

Acquit copper before start of trial – that’s easy to understand (5-3)

Solution – clear cut

If something is clear cut you could say it was "easy to understand"

And you can get to clear cut from the first part of the clue like this;

Acquit = clear
Copper = cu (the chemical symbol)
Start of trial = the first letter of trial ie t

Clear cu+t = clear cut