Article horde rotated in vault is WMD (4,4)
I believe the answer is:
atom bomb
'article horde' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'rotated in vault is wmd' is the wordplay.
I cannot really see how this works, but
'vault' could be 'tomb' (I've seen this before) and 'tomb' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for atom bomb that I've seen before include "Nuclear device" , "Nuclear weapon" , "Big weapon" , "Destructive weapon" , "It would deter" .)