Actually it's more than a little brook (4)
I believe the answer is:
ebro
'actually it's more' is the definition.
I can't judge whether this defines the answer.
'a little brook' is the wordplay.
'EBRO' is hidden within the letters.
But, I'm not sure how this is indicated.
'than' is the link.
Can you help me to learn more?
(Other definitions for ebro that I've seen before include "that's streaming in Spain?" , "Iberian river" , "foreign river" , "Border Hannibal crossed" , "River of northeast Spain" .)