Master managed flow (6)
I believe the answer is:
stream
'flow' is the definition.
(stream is a kind of flow)
'master managed' is the wordplay.
'managed' indicates anagramming the letters.
'master' anagrammed gives 'STREAM'.
(Other definitions for stream that I've seen before include "Current - file" , "Torrent" , "Transmit music or video online" , "Small watercourse" , "Running liquid" .)