Farewell note that Japanese put on the floor (6)
I believe the answer is:
tatami
'that japanese put on the floor' is the definition.
(traditional Japanese floor covering)
'farewell note' is the wordplay.
'farewell' becomes 'tata' (I've seen this before).
'note' becomes 'mi' (as in 'do re mi').
'tata'+'mi'='TATAMI'
(Other definitions for tatami that I've seen before include "Jap. floor mat" , "Jap. room matting" , "Japanese straw mat; a mat, it (anag.)" , "Japanese rush and straw matting" , "Floor-covering" .)