Uncle finishes a bit of work in the sedentary line (5)
I believe the answer is:
clerk
'uncle' is the definition.
The answer and definition can be both people as well as being singular nouns.
Maybe there's a link between them I don't understand?
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for clerk that I've seen before include "Record-keeper" , "'One keeps records, files etc (5)'" , "Record- or account-keeper" , "Office/bank worker" , "Office menial" .)