Get on with head of corporation in New York office (6)
I believe the answer is:
agency
'office' is the definition.
('agency' can be a synonym of 'office')
'get on with head of corporation in new york' is the wordplay.
'get on' becomes 'age' ('age' can be a synonym of 'get on').
'with' means one lot of letters go next to another.
'head of' says to take the initial letters.
'in' indicates putting letters inside.
'new york' becomes 'ny'.
The initial letter of 'corporation' is 'c'.
'c' inserted within 'ny' is 'ncy'.
'age'+'ncy'='AGENCY'
(Other definitions for agency that I've seen before include "Business that represents actors etc." , "Business serving other businesses" , "Cagney (anag.)" , "Organisation; intervention" , "Recruiters possibly" .)