Drain for the rain in Spain (4)
I believe the answer is:
'drain for the rain in spain' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ebro that I've seen before include "European river" , "foreign river" , "Longest river in Spain" , "River of NE Spain; bore (anag.)" , "Spanish runner" .)