Opposite of "high" (3)
I believe the answer is:
low
'opposite of high' is the definition.
(I know this)
This is all the clue.
(Other definitions for low that I've seen before include "Humble; dejected" , "Unimportant sort of owl" , "Depressed; moo" , "Depressed; near the ground" , "Inferior, cow's call" .)