Gradually become smaller (4)
I believe the answer is:
wane
(Other definitions for wane that I've seen before include "Anew (anag.)" , "Decline or go down" , "Get smaller" , "Become smaller" , "Decrease (like the moon)" .)
I believe the answer is:
wane
(Other definitions for wane that I've seen before include "Anew (anag.)" , "Decline or go down" , "Get smaller" , "Become smaller" , "Decrease (like the moon)" .)