Gentle movement of air (4)
I believe the answer is:
waft
'gentle movement of air' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for waft that I've seen before include "Sail" , "Be borne on breeze" , "Drift (like a faint smell)" , "Propel lightly" , "Float on breeze" .)