Some security personnel use keys (4)
I believe the answer is:
type
'use keys' is the definition.
(type with a keyboard)
'some security personnel' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'TYPE' is hidden in the letters of 'security personnel'.
(Other definitions for type that I've seen before include "key" , "Mark" , "Sort; printed letters" , "Courier for example" , "Write letters" .)