Backed wisdom gathered about northern register (5)
I believe the answer is:
enrol
'register' is the definition.
(enrolling is a kind of registering)
'backed wisdom gathered about northern' is the wordplay.
'backed' says the letters should be written backwards.
'wisdom' becomes 'lore' (I've seen this before).
'gathered' is an insertion indicator.
'about northern' becomes 'n' (abbreviation e.g. N. Ireland. I am not sure about the 'about' bit.).
'lore' going around 'n' is 'lorne'.
'lorne' reversed gives 'ENROL'.
Can you help me to learn more?
(Other definitions for enrol that I've seen before include "Join as member" , "Loner inclined to join in" , "register for classes" , "Register (as member)" , "Register officially" .)