Greek city's grain brought across current Turkish borders (7)
I believe the answer is:
corinth
'greek city's' is the definition.
(I've seen this before)
'grain brought across current turkish borders' is the wordplay.
'grain' becomes 'corn' (corn is a kind of grain).
'brought across' means one lot of letters goes inside another (some letters are brought around or across others).
'current' becomes 'I' (symbol for electric current).
'borders' means to remove the middle letters (only the edge or border letters remain).
'turkish' with its centre taken out is 'th'.
'corn' going around 'i' is 'corin'.
'corin'+'th'='CORINTH'
(Other definitions for corinth that I've seen before include "Greek Gulf, isthmus city" , "City of Greece" , "Mediterranean port" , "Greek port and city, important since classical times" , "Region of ancient Greece" .)