Observe article, displaying extreme anger (8)
I believe the answer is:
seething
'displaying extreme anger' is the definition.
'observe article' is the wordplay.
'observe' becomes 'see' (I've seen this before).
'article' becomes 'thing' (I've seen this before).
'see'+'thing'='SEETHING'
(Other definitions for seething that I've seen before include "Furious" , "coming to the boil?" , "making one very angry" , "Boiling" , "very hot" .)