Stranger died in north European river (5)
I believe the answer is:
odder
'stranger' is the definition.
(I've seen this before)
'died in north european river' is the wordplay.
'died' becomes 'd'.
'in' indicates putting letters inside.
'north european river' becomes 'oder' (central European river).
'd' going within 'oder' is 'ODDER'.
(Other definitions for odder that I've seen before include "More strange or less even" , "more rum" , "More unusual" , "More peculiar" , "Stranger" .)