Notice object discreetly boiling (8)
I believe the answer is:
seething
'boiling' is the definition.
('seethe' can be a synonym of 'boil')
'notice object discreetly' is the wordplay.
'notice' becomes 'see' (notice can mean to spot or see).
'object discreetly' becomes 'thing' (an object is a thing or item. I am not sure about the 'discreetly' bit.).
'see'+'thing'='SEETHING'
Can you help me to learn more?
(Other definitions for seething that I've seen before include "Bubbling, perhaps with rage" , "making one very angry" , "Observe object - bubbling with rage" , "very hot" , "Furious" .)