Opening screen secures name (4)
I believe the answer is:
vent
'opening' is the definition.
(I know that vent is a type of slit)
'screen secures name' is the wordplay.
'screen' becomes 'vet' (screen can mean to check or vet).
'secures' indicates putting letters inside.
'name' becomes 'n' (common abbreviation e.g. on forms).
'vet' going around 'n' is 'VENT'.
(Other definitions for vent that I've seen before include "Airhole" , "Opening for air" , "Air passage" , "pipe" , "Give outlet as to feelings" .)