Employs guessers now and then (4)
I believe the answer is:
uses
'employs' is the definition.
('use' can be a synonym of 'employ')
'guessers now and then' is the wordplay.
'now and then' indicates alternate letters (letters taken on a regular basis, now and then).
The alternating letters of 'guessers' are 'USES'.
(Other definitions for uses that I've seen before include "Puts into service" , "Puts to a particular purpose" , "Utilises" , "Functions, applications" , "Purposes; consumes" .)