I posted different down payment (7)
I believe the answer is:
deposit
'down payment' is the definition.
(synonyms)
'i posted different' is the wordplay.
'different' indicates an anagram (letters placed in a different order).
'i'+'posted'='iposted'
'iposted' is an anagram of 'DEPOSIT'.
(Other definitions for deposit that I've seen before include "Lay down" , "Money in bank - part payment" , "is one back on the bottle?" , "Plant" , "Returnable sum" .)