River in the mountains (4)
I believe the answer is:
ural
This clue is a double definition.
'river' is the first definition.
(I've seen this before)
'mountains' is the second definition.
(the Ural Mountains)
'in the' is the link.
(Other definitions for ural that I've seen before include "The .... Mountains divide Europe and Asia" , "Runner" , "River of central Russia" , "Mountain range between Europe and Asia" , "Asian flower" .)