Get on with Northern Territory delegate (5)
I believe the answer is:
agent
'delegate' is the definition.
(I've seen this before)
'get on with northern territory' is the wordplay.
'get on' becomes 'age' (synonyms).
'with' is a charade indicator (letters next to each other).
'northern territory' becomes 'nt'.
'age'+'nt'='AGENT'
(Other definitions for agent that I've seen before include "Delegate" , "Operative" , "Go-between" , "that may be secret?" , "Spy - broker" .)