Note the soft sound in the forest (6)
I believe the answer is:
epping
'the forest' is the definition.
(I've seen this before)
'note the soft sound in' is the wordplay.
'note' becomes 'e' (musical note).
'the soft' becomes 'p' (musical abbreviation for 'piano').
'sound' becomes 'ping' (ping is a kind of sound).
'in' indicates putting letters inside.
'p' put inside 'ping' is 'pping'.
'e'+'pping'='EPPING'
(Other definitions for epping that I've seen before include "Forest near London" , "Forest NE of London" , "Essex site of a forest" .)