Make longer part of journey around Norway next (8)
I believe the answer is:
lengthen
'make longer' is the definition.
('lengthen' can be a synonym of 'make longer')
'part of journey around norway next' is the wordplay.
'part of journey' becomes 'leg' ('leg' is part of 'journey').
'around' indicates putting letters inside.
'norway' becomes 'n'.
'next' becomes 'then' (I've seen this before).
'leg' placed around 'n' is 'leng'.
'leng'+'then'='LENGTHEN'
(Other definitions for lengthen that I've seen before include "increase in duration" , "Extend or draw out" , "Spin out" , "Protract" , "Stretch" .)