Cause to flow in a stream (4)
I believe the answer is:
pour
'cause to flow in a stream' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for pour that I've seen before include "Cause to flow as from pot to cup" , "Dispense (e.g. tea)" , "16 [CATS AND DOGS]" , "Teem" , "Tip liquid from container" .)