European runner set bar low at intervals (4)
I believe the answer is:
ebro
'european runner' is the definition.
(I've seen this before)
'set bar low at intervals' is the wordplay.
'at intervals' indicates alternate letters (letters are taken at regular intervals).
'set'+'bar'+'low'='setbarlow'
The alternating letters of 'setbarlow' are 'EBRO'.
(Other definitions for ebro that I've seen before include "that's streaming in Spain?" , "Border Hannibal crossed" , "River of northeast Spain" , "foreign river" , "European river" .)