It brings down the tone when depressed (4,5)
I believe the answer is:
soft pedal
'it brings down' is the definition.
The definition suggests a singular noun which matches the answer.
'tone when depressed' is the wordplay.
I cannot really understand how this works, but
'tone' could be 'pedal' (pedal is a kind of tone) and 'pedal' is present in the answer.
The remaining letters 'soft' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'the' is the link.
Can you help me to learn more?
(Other definitions for soft pedal that I've seen before include "Play down" , "Be restrained, take it easy - on bicycle?" , "forte being fluid" , "moderate" , "piano maker?" .)