Intense anger about northern mountains (5)
I believe the answer is:
range
'mountains' is the definition.
(range of mountains)
'intense anger about northern' is the wordplay.
'intense anger' becomes 'rage' (I've seen this before).
'about' indicates putting letters inside.
'northern' becomes 'n' (abbreviation e.g. N. Ireland).
'rage' enclosing 'n' is 'RANGE'.
(Other definitions for range that I've seen before include "Scope, extent" , "Area for shooting practice" , "Scope; chain" , "Compass, extent" , "Open grazing land or cooking stove" .)