Really go crazy producing a fable (8)
I believe the answer is:
allegory
'a fable' is the definition.
('allegory' can be a synonym of 'fable')
'really go crazy' is the wordplay.
'crazy' is an anagram indicator.
'really'+'go'='reallygo'
'reallygo' anagrammed gives 'ALLEGORY'.
'producing' acts as a link.
(Other definitions for allegory that I've seen before include "Animal Farm, for example" , "Symbolic work" , "Story with symbolic characters" , "Story which symbolizes some deeper meaning" , "Its characters are personifications" .)