Analysis of arsenic, for example (5)
I believe the answer is:
assay
'analysis' is the definition.
(thesaurus)
'arsenic for example' is the wordplay.
'arsenic' becomes 'as' (As is the chemical symbol for arsenic).
'for example' becomes 'say' (I've seen this before).
'as'+'say'='ASSAY'
'of' acts as a link.
(Other definitions for assay that I've seen before include "Examine chemicals" , "Test ore for content" , "Test(ing) of a substance, such as precious metal" , "Test quality of ore" , "Test (a metal or ore)" .)