Rant away as dictionary is revised - such foolishness (6)
I believe the answer is:
idiocy
'foolishness' is the definition.
(I've seen this before)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for idiocy that I've seen before include "Complete folly" , "Chopper" , "Stupid behaviour or talk" , "Foolish act" , "Great folly" .)