Value a quiet expression of approval (8)
I believe the answer is:
appraise
'value' is the definition.
(synonyms)
'a quiet expression of approval' is the wordplay.
'quiet' becomes 'pp' (musical abbreviation for pianissimo).
'expression of approval' becomes 'raise' (I can't explain this - if you can you should give a lot more credence to this answer).
'a'+'pp'+'raise'='APPRAISE'
Can you help me to learn more?
(Other definitions for appraise that I've seen before include "Assess the value/quality of (something)" , "Consider comprehensively" , "Estimate or assess the value of" , "Decide the value or quality of" , "Assess (a thing's) quality" .)