Employer concocted ruse (4)
I believe the answer is:
user
'employer' is the definition.
(thesaurus)
'concocted ruse' is the wordplay.
'concocted' is an anagram indicator.
'ruse' with letters rearranged gives 'USER'.
(Other definitions for user that I've seen before include "Ruse for employer" , "Someone who exploits another" , "Operator (of something)" , "One who employs" , "One getting benefit from" .)