Work shift for many (4)
I believe the answer is:
days
'work shift for many' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for days that I've seen before include "24-hour periods" , "Twenty-four hour periods" , "` `They are not long, the .... of wine and roses' ' (Dowson)" , "Periods of 24 hours" , "Sevenths of a week" .)