Folklore taken from an academy thesis (4)
I believe the answer is:
myth
'folklore' is the definition.
(I've seen this in another clue)
'taken from an academy thesis' is the wordplay.
'taken from' says the answer is hidden in the clue.
'MYTH' can be found hidden inside 'academy thesis'.
(Other definitions for myth that I've seen before include "Wildly-held but false belief or idea" , "Ancient story" , "a false notion" , "Invention" , "There's no truth in it" .)