Transplant is hard work (5)
I believe the answer is:
graft
This clue is a double definition.
'transplant' is the first definition.
(I know that transplant can be written as graft)
'is hard work' is the second definition.
(graft can mean working hard)
(Other definitions for graft that I've seen before include "Slip" , "Hard work - corrupt profit" , "Hard work; bribery" , "Surgical transplant" , "Make parts of different plants grow together" .)