Material from northern banker (5)
I believe the answer is:
tweed
'material' is the definition.
(I know that tweed is a type of material)
'from northern banker' is the wordplay.
'from' becomes 'tw' (I am not sure about this - if you are sure you should believe this answer much more).
'northern' is a reversal indicator (in a down clue, letters go up or 'north').
'banker' becomes 'dee' (I've seen this in other clues).
'dee' back-to-front is 'eed'.
'tw'+'eed'='TWEED'
Can you help me to learn more?
(Other definitions for tweed that I've seen before include "Flower on border" , "Harris cloth" , "passes between English and Scottish banks" , "Fabric; river" , "Scottish/English river" .)