States old city president to take over (5)
I believe the answer is:
usurp
'take over' is the definition.
(I know that take over can be written as usurp)
'states old city president' is the wordplay.
'states' becomes 'US' (abbreviation for the United States).
'old city' becomes 'ur' (ancient city state).
'president' becomes 'p' (common abbreviation eg in VP).
'us'+'ur'+'p'='USURP'
'to' acts as a link.
(Other definitions for usurp that I've seen before include "Assume by force" , "Take over occupation" , "Take (power) by force or illegally" , "Seize, take over" , "Seize wrongfully" .)