Ancient Assyrian capital (7)
I believe the answer is:
nineveh
'ancient assyrian capital' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for nineveh that I've seen before include "old city" , "Ancient city on the Tigris" , "Assyrian capital; Jonah preached against it" , "Ancient Assyrian capital" , "Ancient capital of Assyria" .)