Control meandering stream (6)
I believe the answer is:
master
'control' is the definition.
(synonyms)
'meandering stream' is the wordplay.
'meandering' indicates an anagram.
'stream' anagrammed gives 'MASTER'.
(Other definitions for master that I've seen before include "Lord - controller - teacher" , "Subdue, win over" , "Instructor" , "Dominate" , "Skilled practitioner" .)