President Trump primarily working in northern city (7)
I believe the answer is:
preston
'northern city' is the definition.
(city in the north of England)
'president trump primarily working' is the wordplay.
'president' becomes 'p' (common abbreviation eg in VP).
'trump primarily' becomes 'rest' (I can't justify this - if you can you should give a lot more credence to this answer).
'working' becomes 'on' (e.g. a machine is working or on).
'p'+'rest'+'on'='PRESTON'
'in' is the link.
Can you help me to learn more?
(Other definitions for preston that I've seen before include "Town on the Ribble" , "town in northern England" , "Administrative centre of Lancashire" , "city (as of 2002)" , "City in Lancashire" .)