Organ -- new make (4)
I believe the answer is:
'make' is the definition.
('earn' can be a synonym of 'make')
'organ new' is the wordplay.
'organ' becomes 'ear' (ear is a kind of organ).
'new' becomes 'n'.
(Other definitions for earn that I've seen before include "Gain by work or effort" , "Pull in" , "Win" , "Make - merit" , "Be paid for work" .)