Bishop, extremely aghast, interrupts innocent story (9)
I believe the answer is:
narrative
'story' is the definition.
(I know that story can be written as narrative)
'bishop extremely aghast interrupts innocent' is the wordplay.
'bishop' becomes 'rr' (abbreviation for Right Reverend).
'extremely aghast' becomes 'at' (I am not sure about this - if you are sure you should believe this answer much more).
'interrupts' is an insertion indicator.
'innocent' becomes 'naive' (similar in meaning).
'rr'+'at'='rrat'
'rrat' going inside 'naive' is 'NARRATIVE'.
Can you help me to learn more?
(Other definitions for narrative that I've seen before include "Popeye's vegetable" , "Account of connected events, a story" , "Verbal account" , "Tale" , "Chronicle" .)