Stream must be present (7)
I believe the answer is:
current
I believe this clue is a double definition.
'stream' is the first definition.
(I know that stream can be written as current)
'present' is the second definition.
(similar in meaning)
'must be' is the link.
(Other definitions for current that I've seen before include "Happening now" , "Of the present time" , "Popular" , "flower" , "In general use; flow" .)