Implantation is hard work (5)
I believe the answer is:
graft
I believe this is a double definition.
'implantation' is the first definition.
(thesaurus)
'is hard work' is the second definition.
(graft can mean working hard)
(Other definitions for graft that I've seen before include "Slip" , "Means of propagation - hard work?" , "Hard work; bribery" , "Transplant - hard work" , "Hard work - swindle" .)