Employed in refuse disposal (4)
I believe the answer is:
used
'employed' is the definition.
('use' can be a synonym of 'employ')
'in refuse disposal' is the wordplay.
'in' says the answer is hidden in the clue.
'USED' can be found hidden inside 'refuse disposal'.
(Other definitions for used that I've seen before include "Brought into play" , "Scottish expert" , "Second-hand; exploited" , "Sued, having been employed" , "with a previous owner" .)