Keeps circling quiet trees, deriving pleasure (9)
I believe the answer is:
happiness
'pleasure' is the definition.
(thesaurus)
'keeps circling quiet trees deriving' is the wordplay.
'keeps' becomes 'has' (keep can mean to have or possess).
'circling' is an insertion indicator (circling can mean going around or containing).
'quiet' becomes 'pp' (musical abbreviation for pianissimo).
'trees deriving' becomes 'ines' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'pp'+'ines'='ppines'
'has' enclosing 'ppines' is 'HAPPINESS'.
Can you help me to learn more?
(Other definitions for happiness that I've seen before include "Enjoyment" , "Great contentment" , "Joy, well-being," , "Cheer" , "Felicity" .)