A nobleman has penned conclusion of epic story (7)
I believe the answer is:
account
'story' is the definition.
(synonyms)
'a nobleman has penned conclusion of epic' is the wordplay.
'nobleman' becomes 'count' (count is a kind of nobleman).
'has penned' is an insertion indicator (inserted letters are enclosed or penned in).
'conclusion of' suggests the final letters.
The last letter of 'epic' is 'c'.
'count' enclosing 'c' is 'ccount'.
'a'+'ccount'='ACCOUNT'
(Other definitions for account that I've seen before include "Bank record" , "Financial record; narrative" , "books" , "Bill; description" , "Bill - relation" .)