Client US employer cleaned out (4)
I believe the answer is:
user
'client' is the definition.
(I've seen this in another clue)
'us employer cleaned out' is the wordplay.
'cleaned out' suggests removing the centre.
'employer' with its middle taken out is 'er'.
'us'+'er'='USER'
(Other definitions for user that I've seen before include "Junkie's" , "Right long-established" , "One who works an appliance" , "One taking advantage" , "Someone who exploits another" .)