Five-day trials? (5)
I believe the answer is:
tests
'trials?' is the definition.
(I know this)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for tests that I've seen before include "Tries out" , "Major cricket matches" , "Examinations, trials" , "Trials to see if something works" , "Trials, exams" .)