Refers to a person coming up, and worse executing a presumed to be brilliant strategy, often predicated on the other side being too naïve or unintelligent to realise it or counter it – the stratagem usually results in disaster.
In popular media the “cunning plan” offered by the character Baldrick to his master in the Blackadder series is a ridiculous and overly complicated scheme devised by the dim-witted character, indeed the elaborate plans devised by Blackadder himself might be characterised as an ‘attack of the clevers.’