Make smaller (6)
'make smaller' is the definition.
(reducing is a kind of making smaller)
This is all the clue.
(Other definitions for reduce that I've seen before include "Lower" , "Shrink" , "Make or become smaller" , "Of a sauce, thicken" , "subdue" .)
'make smaller' is the definition.
(shrinking is a kind of making smaller)
This is the entire clue.
(Other definitions for shrink that I've seen before include "Reduce in size" , "Grow smaller like slangy psychiatrist" , "Get smaller - psychiatrist" , "Become smaller like slang psychiatrist" , "Shrivel" .)