Joy has to keep quiet and languishes (9)
I believe the answer is:
happiness
'joy' is the definition.
(thesaurus)
'has to keep quiet and languishes' is the wordplay.
'to keep' is an insertion indicator.
'quiet' becomes 'p' (music symbol for 'piano').
'and' means one lot of letters go next to another.
'languishes' becomes 'pines' ('pine' can be a synonym of 'languish'**).
'p'+'pines'='ppines'
'has' going around 'ppines' is 'HAPPINESS'.
(Other definitions for happiness that I've seen before include "Joy, well-being," , "Contentment, joy" , "Felicity" , "Enjoyment" , "State of well-being, contentment" .)