A risk originally found in shiny appendix (8)
I believe the answer is:
glossary
'appendix' is the definition.
(I've seen this before)
'a risk originally found in shiny' is the wordplay.
'originally' says to take the initial letters.
'found in' means one lot of letters goes inside another.
'shiny' becomes 'glossy' ('glossy' can be a synonym of 'shiny'**).
The initial letter of 'risk' is 'r'.
'a'+'r'='ar'
'ar' going inside 'glossy' is 'GLOSSARY'.
(Other definitions for glossary that I've seen before include "List of explanations of words" , "List of technical words with definitions" , "Specialised dictionary" , "List of technical terms in an appendix" , "Explanatory list of words" .)