Rejected masquerade by adult storyteller (5)
I believe the answer is:
aesop
'storyteller' is the definition.
(Aesop is an example)
'rejected masquerade by adult' is the wordplay.
'rejected' shows that the letters should be reversed in order.
'masquerade by' becomes 'pose' (I can't justify this - if you can you should give a lot more credence to this answer).
'adult' becomes 'a'.
'pose'+'a'='posea'
'posea' backwards is 'AESOP'.
Can you help me to learn more?
(Other definitions for aesop that I've seen before include "Fabulous man" , "Fable-teller" , "Fabulous writer" , "very old writer" , "fabulous figure?" .)