Old tree, largely hollow (7)
I believe the answer is:
elderly
'old' is the definition.
('elderly' can be similar in meaning to 'old')
'tree largely hollow' is the wordplay.
'tree' becomes 'elder' (elder is a kind of tree**).
'hollow' means to remove the middle letters.
'largely' with its middle taken out is 'ly'.
'elder'+'ly'='ELDERLY'
(Other definitions for elderly that I've seen before include "Quite old" , "... or not of tender years" , "over the hill" , "Long in the tooth" , "like a rich attorney's ugly daughter" .)