Employs Aussies so regularly (4)
I believe the answer is:
uses
'employs' is the definition.
('use' can be a synonym of 'employ')
'aussies so regularly' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'aussies'+'so'='aussiesso'
The alternate letters of 'aussiesso' are 'USES'.
(Other definitions for uses that I've seen before include "Employs" , "'Purposes, functions (4)'" , "deployments" , "Customs" , "Sues (anag.)" .)