Articles granny pens primarily in Greek (8)
I believe the answer is:
athenian
'greek' is the definition.
(I know that Athenian is a type of greek)
'articles granny pens primarily in' is the wordplay.
'articles' becomes 'athe' ('a' and 'the', indefinite and definite articles).
'granny' becomes 'nan'.
'pens' means one lot of letters goes inside another (to pen can mean to contain or imprison).
'primarily' indicates taking the first letters.
The first letter of 'in' is 'i'.
'nan' going around 'i' is 'nian'.
'athe'+'nian'='ATHENIAN'
(Other definitions for athenian that I've seen before include "of capital city" , "Inhabitant of Greek capital" , "Denizen of Greek capital" , "Native of Greek capital" , "Nationality of citizen of Greek capital" .)