Some chores unfortunately upset employer (4)
I believe the answer is:
user
'employer' is the definition.
(I've seen this before)
'some chores unfortunately upset' is the wordplay.
'some' says the answer is hidden in the clue (some of the parts of the word are used).
'upset' shows that the letters should be reversed in order.
'resu' is hidden in the letters of 'chores unfortunately'.
'resu' backwards is 'USER'.
(Other definitions for user that I've seen before include "Exploiter (of others)" , "Tech support caller?" , "One getting benefit from" , "Drug addict (informal)" , "One operating something" .)