Observe article, and fume! (6)
I believe the answer is:
seethe
'fume' is the definition.
(I've seen this before)
'observe article' is the wordplay.
'observe' becomes 'see' (observe can mean to see something).
'article' becomes 'the' (the definite article in English).
'see'+'the'='SEETHE'
'and' acts as a link.
(Other definitions for seethe that I've seen before include "Surge or foam, as if boiling" , "Steep - surge" , "Bubble away" , "Bubble gently like boiling water" , "Be silently angry" .)