So detective appears in long story divided into several parts (8)
I believe the answer is:
episodic
'divided into several parts' is the definition.
(split into episodes)
'so detective appears in long story' is the wordplay.
'detective' becomes 'di' (Detective Inspector abbreviation).
'appears in' means one lot of letters goes inside another.
'long story' becomes 'epic' (I've seen this before).
'so'+'di'='sodi'
'sodi' going into 'epic' is 'EPISODIC'.
(Other definitions for episodic that I've seen before include "Sporadic" , "piecemeal" , "Occurring at irregular intervals" , "in serial form" , "Occurring irregularly - is copied accordingly" .)