Story of mine that's originally hard to follow (4)
I believe the answer is:
myth
'story' is the definition.
(I know that myth is a type of story)
'mine that's originally hard to follow' is the wordplay.
'mine' becomes 'my'.
'originally' indicates taking the first letters.
'hard' becomes 'h' (abbreviation used in pencil classifications).
'to follow' means one lot of letters go next to another (some letters go after or follow others).
The initial letter of 'that' is 't'.
'my'+'t'+'h'='MYTH'
'of' acts as a link.
(Other definitions for myth that I've seen before include "Ancient story" , "Invention" , "Fiction" , "Fictitious thing; traditional story" , "Story of old gods" .)