Old tree with lovely leaves (7)
I believe the answer is:
elderly
'old' is the definition.
(I know that old can be written as elderly)
'tree with lovely leaves' is the wordplay.
'tree' becomes 'elder' (elder is a kind of tree).
'with lovely leaves' becomes 'ly' (I am not sure about this - if you are sure you should believe this answer much more).
'elder'+'ly'='ELDERLY'
Can you help me to learn more?
(Other definitions for elderly that I've seen before include "Silver" , "... or not of tender years" , "Rather old" , "Of advanced years" , "Aged" .)