Employs some house-sitters (4)
I believe the answer is:
uses
'employs' is the definition.
('use' can be a synonym of 'employ')
'some house-sitters' is the wordplay.
'some' says the answer is hidden in the clue (some of the parts of the word are used).
'USES' can be found hidden inside 'house sitters'.
(Other definitions for uses that I've seen before include "Purposes; consumes" , "Consumes; treats" , "Takes (drugs)" , "'Purposes, functions (4)'" , "Exercises" .)