One who studies for each employer (7)
I believe the answer is:
peruser
'one who studies' is the definition.
The definition suggests a singular noun which matches the answer.
'each employer' is the wordplay.
'each' becomes 'per' ('per' can mean for each).
'employer' becomes 'user' (someone who employs or uses something).
'per'+'user'='PERUSER'
'for' is the link.
Can you help me to learn more?
(Other definitions for peruser that I've seen before include "Rep rues meeting a reader" , "One studying" , "Scanner" , "One examining" , "one reads" .)