Join Labour (5)
I believe the answer is:
graft
I believe this is a double definition.
'join' is the first definition.
(I know that graft is a more specific form of the action join)
'labour' is the second definition.
(I've seen this before)
(Other definitions for graft that I've seen before include "Make parts of different plants grow together" , "Transplant - hard work" , "Hard work; corruption" , "Make money from corruption" , "Transfer of tissue - hard work!" .)