It's hard work getting a good right back (5)
I believe the answer is:
graft
'it's hard work' is the definition.
(I've seen this before)
'a good right back' is the wordplay.
'a good' becomes 'g' (abbreviation).
'right' becomes 'r' (common abbreviation).
'back' becomes 'aft' (associated in meaning).
'g'+'r'+'aft'='GRAFT'
'getting' is the link.
(Other definitions for graft that I've seen before include "Make parts of different plants grow together" , "Hard work - corrupt profit" , "Means of propagation - hard work?" , "Make money from corruption" , "Hard work; bribery" .)