Quite happy with a rented piano (7)
I believe the answer is:
pleased
'piano' is the definition.
Both the definition and answer are adjectives. Maybe you can see an association between them that I don't see?
'quite happy with a rented' is the wordplay.
'quite happy' becomes 'p' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'with' is a charade indicator (letters next to each other).
'a rented' becomes 'leased' (I've seen this before).
'p'+'leased'='PLEASED'
Can you help me to learn more?
(Other definitions for pleased that I've seen before include "like Punch?" , "Glad" , "Gratified" , "Feeling satisfaction" , "Grateful, delighted" .)