Begin to wake (4)
I believe the answer is:
stir
'begin to wake' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for stir that I've seen before include "Prison - mix" , "Prison (sl.); agitate" , "Whisk or whip" , "created by an agitator?" , "move very slightly, or agitate" .)