Managed company with old city hostility (7)
I believe the answer is:
rancour
'hostility' is the definition.
(I know that rancour is a type of hostility)
'managed company with old city' is the wordplay.
'managed' becomes 'ran' (both can mean organised or was in charge of).
'company' becomes 'co' (abbreviation).
'with' means one lot of letters go next to another.
'old city' becomes 'ur' (ancient city state).
'ran'+'co'+'ur'='RANCOUR'
(Other definitions for rancour that I've seen before include "Animosity" , "Deep, bitter hate" , "Bad feeling and resentment" , "Bitter resentment" , "Bitter feeling or ill-will" .)