Depend on receiving a soft answer (5)
I believe the answer is:
Here is my best explanation:
'answer' is the definition.
'depend on receiving a soft' is the wordplay.
'depend on' becomes 'rely' (I've seen this before).
'receiving' means one lot of letters goes inside another.
'a soft' becomes 'p' (musical abbreviation for 'piano').
'rely' enclosing 'p' is 'REPLY'.