US city sure to secure a win (7)
I believe the answer is:
oakland
'us city' is the definition.
(I've seen this before)
'sure to secure a win' is the wordplay.
'sure' becomes 'ok' (both are affirmative answers).
'to secure' means one lot of letters goes inside another (inserted letters are secured inside).
'win' becomes 'land' (both can mean to secure or obtain).
'ok' placed around 'a' is 'oak'.
'oak'+'land'='OAKLAND'
(Other definitions for oakland that I've seen before include "American port" , "Seaport near San Francisco, and Raiders" , "city in California" , "US port" , "US city" .)