City people originally rely on (7)
I believe the answer is:
preston
'city' is the definition.
(city in Lancashire)
'people originally rely on' is the wordplay.
'originally' suggests taking the first letters.
'rely' becomes 'rest' (rely can mean to rest or depend on).
The initial letter of 'people' is 'p'.
'p'+'rest'+'on'='PRESTON'
(Other definitions for preston that I've seen before include "Town in Lancashire" , "English city" , "Administrative centre of Lancashire" , "Town on the Ribble" , "City in Lancashire" .)