European river rising high in north Estonia, primarily (5)
I believe the answer is:
rhine
'european river' is the definition.
(river in Europe)
'rising high in north estonia primarily' is the wordplay.
'primarily' says to take the initial letters.
The first letters of 'rising high in north estonia' is 'RHINE'.
(Other definitions for rhine that I've seen before include "River flowing from Switzerland, through Germany, to the North Sea" , "River at Bonn, Koln" , "Major European river" , "Great river in Germany with Lorelei Rock" , "River of Cologne" .)