Individually probing trial case (3,5)
I believe the answer is:
tea chest
'case' is the definition.
(thesaurus)
'individually probing trial' is the wordplay.
'individually' becomes 'each' (I've seen this before).
'probing' is an insertion indicator (probe can mean to make a hole in).
'trial' becomes 'test' (synonyms).
'each' put within 'test' is 'TEA-CHEST'.
(Other definitions for tea chest that I've seen before include "Dry container" , "Item famously thrown overboard" , "Light metal-lined box for transportation" , "Box for Earl Grey, perhaps?" , "Foil-lined wooden box" .)