Notes suggest a down payment (7)
I believe the answer is:
deposit
'a down payment' is the definition.
(synonyms)
'notes suggest' is the wordplay.
'notes' becomes 'de' (two musical notes).
'suggest' becomes 'posit' (I've seen this in another clue).
'de'+'posit'='DEPOSIT'
(Other definitions for deposit that I've seen before include "Posited as down payment" , "Down payment made to secure goods" , "I posted (anag.)" , "Sediment or bank lodgment" , "(Money) laid down" .)