Corruption is hard work (5)
I believe the answer is:
graft
This clue is a double definition.
'corruption' is the first definition.
(I've seen this in another clue)
'is hard work' is the second definition.
(graft can mean working hard)
(Other definitions for graft that I've seen before include "Hard work; bribery" , "Hard work; corruption" , "Make money from corruption" , "Transfer of tissue - hard work!" , "Surgical transplant" .)