Ruin Pluto’s flower (8)
I believe the answer is:
disaster
'ruin' is the definition.
The answer and definition can be both acts as well as being singular nouns.
Maybe you can see an association between them that I don't see?
'pluto's flower' is the wordplay.
'pluto' becomes 'dis' (another name for the mythical god).
'flower' becomes 'aster' (aster is a kind of flower).
'dis'+'aster'='DISASTER'
Can you help me to learn more?
(Other definitions for disaster that I've seen before include "Heavy blow" , "terrible trouble" , "Calamity, sudden great misfortune" , "Calamity, tragedy" , "Extreme ruin or misfortune" .)