What's needed for transplants is hard work (5)
I believe the answer is:
graft
This clue is a double definition.
'what's needed for transplants' is the first definition.
(as in a skin graft)
'is hard work' is the second definition.
(graft can mean working hard)
(Other definitions for graft that I've seen before include "Transfer of tissue - hard work!" , "Labour" , "Hard work - corrupt profit" , "Hard work; corruption" , "Make money from corruption" .)