Seeing return of predator, run! (4)
I believe the answer is:
Here is my best explanation:
'run' is the definition.
('flow' can be a synonym of 'run')
'seeing return of predator' is the subsidiary indication.
'seeing return of' says the letters should be written in reverse.
'predator' becomes 'wolf'.
'wolf' in reverse letter order is 'flow'.
(Other definitions for flow that I've seen before include "run", "Well forth", "Run or move like a liquid", "Move along as a stream", "Wolf (anag.)", "Move steadily", "Fluid motion", "Move as liquid", "(Forward) movement of liquid" and "Current".)