Swallow or dove circling over ancient city (6)
I believe the answer is:
devour
'swallow' is the definition.
(thesaurus)
'dove circling over ancient city' is the wordplay.
'circling' is an anagram indicator.
'over' says to put letters next to each other (in a down clue, some letters go over others).
'ancient city' becomes 'ur' (ancient Sumerian city state).
'dove' is an anagram of 'devo'.
'devo'+'ur'='DEVOUR'
'or' acts as a link.
(Other definitions for devour that I've seen before include "Guzzle" , "Eat greedily" , "Swallow greedily" , "Quickly consume" , "Gobble up greedily" .)