No river attended by the navy in the Arctic? (8)
I believe the answer is:
northern
'arctic?' is the definition.
(northern can mean relating to the arctic region)
'no river attended by the navy' is the wordplay.
'river' becomes 'r' (abbreviation for river).
'attended by' is a charade indicator (letters next to each other).
'navy' becomes 'RN' (abbreviation for Royal Navy).
'no'+'r'+'the'+'rn'='NORTHERN'
'in the' acts as a link.
(Other definitions for northern that I've seen before include "Arctic - polar" , "Arctic, boreal" , "Line represented in black on the Tube map" , "Part of the UK" , "Not in or from the south" .)