Test, for example, taken twice (5)
I believe the answer is:
assay
'test' is the definition.
(I know that assay is a type of test)
'example taken twice' is the wordplay.
'example' becomes 'as' (I've seen this in other clues).
'taken twice' becomes 'say' (I can't justify this - if you can you should believe this answer much more).
'as'+'say'='ASSAY'
'for' acts as a link.
Can you help me to learn more?
(Other definitions for assay that I've seen before include "Test, check" , "Test quality of metals" , "Test for metal content" , "Test gold" , "Evaluate" .)