Northerner, no adult on course (4)
I believe the answer is:
scot
'northerner' is the definition.
(I've seen this before)
'no adult on course' is the wordplay.
'no adult' becomes 'cot' (I can't explain this - if you can you should give a lot more credence to this answer).
'on' says to put letters next to each other.
'course' becomes 's'.
'cot' put after 's' is 'SCOT'.
Can you help me to learn more?
(Other definitions for scot that I've seen before include "One from north of the border" , "Native of Inverness" , "Burns for one" , "Highlander perhaps" , "Native of Caledonia" .)