Storm around northern mountains (5)
I believe the answer is:
range
'mountains' is the definition.
(I've seen this before)
'storm around northern' is the wordplay.
'storm' becomes 'rage' ('rage' can be a synonym of 'storm').
'around' is an insertion indicator.
'northern' becomes 'n' (abbreviation e.g. N. Ireland).
'rage' placed around 'n' is 'RANGE'.
(Other definitions for range that I've seen before include "Series of connected mountains" , "area for stock" , "Number of items in a series" , "Vocal compass" , "Sierra" .)