Knock out temporarily (4)
I believe the answer is:
stun
'knock out temporarily' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for stun that I've seen before include "Daze, stupify" , "Daze, knock senseless" , "Shock or astonish" , "Confuse" , "'Shock, daze (4)'" .)