Quiet freedom is commonplace (9)
I believe the answer is:
platitude
'commonplace' is the definition.
(I've seen this before)
'quiet freedom' is the wordplay.
'quiet' becomes 'p' (music symbol for 'piano').
'freedom' becomes 'latitude' (latitude is a kind of freedom).
'p'+'latitude'='PLATITUDE'
'is' acts as a link.
(Other definitions for platitude that I've seen before include "Familiar tune" , "Commonplace remark uttered as if original" , "bromide" , "that says nothing new" , "Empty remark" .)