Unpaid work: Shakespeare’s was lost (6,2,4)
I believe the answer is:
labour of love
I believe this clue is a double definition.
'unpaid work' is the first definition.
(work done without expectation of reward)
'shakespeare's was lost' is the second definition.
(as in Love's Labour's Lost by Shakespeare)
(Other definitions for labour of love that I've seen before include "Task one enjoys" , "Task done for pleasure not money" , "Task undertaken for enjoyment" , "One not undertaken for advantage" , "Work performed voluntarily without hope of material reward" .)