A silent part of the forest (3)
I believe the answer is:
ash
'part of the forest' is the definition.
'ash' can be an answer for 'part' (I have seen 'Part of forest' mean 'ash' so perhaps 'part' could also mean 'ash'). I'm unsure of the 'of the forest' bit.
'a silent' is the wordplay.
'silent' becomes 'sh' (I am not sure about this - if you are sure you should believe this answer much more).
'a'+'sh'='ASH'
Can you help me to learn more?
(Other definitions for ash that I've seen before include "Hardwood" , "Grey colour" , "Tree; fire residue" , "Tree with keys" , "Timber tree" .)