Case involves every one in a trial (3,5)
I believe the answer is:
tea chest
'case' is the definition.
(thesaurus)
'every one in a trial' is the wordplay.
'every one' becomes 'each' (I've seen this in other clues).
'in' indicates putting letters inside.
'a trial' becomes 'test' ('test' can be a synonym of 'trial').
'each' going within 'test' is 'TEA-CHEST'.
'involves' is the link.
This may not be right. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for tea chest that I've seen before include "box exported from India?" , "packing-case" , "Dry container" , "Box for Earl Grey, perhaps?" , "case for move" .)