Measure up to leading north-eastern district (4)
I believe the answer is:
zone
'district' is the definition.
(I know that district can be written as zone)
'measure up to leading north-eastern' is the wordplay.
'measure' becomes 'oz' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'to leading' is a charade indicator (letters next to each other) (some letters go in front of others).
'north eastern' becomes 'NE' (abbreviation).
'oz' back-to-front is 'zo'.
'zo'+'ne'='ZONE'
Can you help me to learn more?
(Other definitions for zone that I've seen before include "Marked area" , "Area subject to restrictions, parking say" , "A defined area as for particular purpose" , "London Underground region" , "Section" .)