Loud, competent story (5)
I believe the answer is:
fable
'story' is the definition.
(fable is a kind of story)
'loud competent' is the wordplay.
'loud' becomes 'f' (short for forte - 'loud' in music).
'competent' becomes 'able' (similar in meaning).
'f'+'able'='FABLE'
(Other definitions for fable that I've seen before include "there may be a moral to it" , "Moral tale" , "Aesop story" , "One of Aesop's tales" , "Aesop's story?" .)