Test contents of case, for example (5)
I believe the answer is:
assay
'test' is the definition.
(synonyms)
'contents of case for example' is the wordplay.
'contents of' indicates the central letters (letters inside the word).
'for example' becomes 'say' ('say' can be used to introduce an example).
The central letters of 'case' are 'as'.
'as'+'say'='ASSAY'
(Other definitions for assay that I've seen before include "Test (a metal or ore)" , "Test, check" , "Test quality of ore" , "Check (a metal's) quality" , "Examine chemicals" .)