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 tell whether this defines the answer.
'a little brook' is the wordplay.
'EBRO' is hidden in amongst the letters.
But, I am unsure how the hidden word 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" .)