Author in store with novel penned by Greek (11)
I believe the answer is:
ghostwriter
'author' is the definition.
(ghostwriter is a kind of author)
'store with novel penned by greek' is the wordplay.
'novel' indicates anagramming the letters.
'penned by' indicates putting letters inside.
'greek' becomes 'gr'.
'store'+'with'='storewith'
'storewith' is an anagram of 'hostwrite'.
'hostwrite' inserted into 'gr' is 'GHOSTWRITER'.
'in' is the link.
(Other definitions for ghostwriter that I've seen before include "Author denied credit" , "Maybe Sheridan Le Fanu" , "second involved in an autobiography?" , "scibe for the incapable" .)