Employer's sure to adapt (4)
I believe the answer is:
user
'employer's' is the definition.
(someone who employs or uses something)
'sure to adapt' is the wordplay.
'to adapt' indicates anagramming the letters (I've seen 'adapting' mean this).
'sure' with letters rearranged gives 'USER'.
(Other definitions for user that I've seen before include "Exploiter (of others)" , "Operator; exploiter" , "Tech support caller?" , "One getting benefit from" , "one has to employ" .)