Father's flat note (5)
I believe the answer is:
padre
'father's' is the definition.
('Padre' can be a synonym of 'father')
'flat note' is the wordplay.
'flat' becomes 'pad' (person's home).
'note' becomes 're'.
'pad'+'re'='PADRE'
(Other definitions for padre that I've seen before include "Army chaplain" , "A military clergyman" , "Military chaplain" , "Services' chaplain" , "Cleric" .)