Slight wave (6)
I believe the answer is:
ripple
'slight wave' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for ripple that I've seen before include "Slight disturbance on water's surface" , "A small wave, or a gentle sound as of laughter" , "undulation" , "Light ruffle on the surface" , "Edgar Allan ---, US author" .)