Approval about a tree (3)
I believe the answer is:
oak
'tree' is the definition.
(oak is a type of tree)
'approval about a' is the wordplay.
'approval' becomes 'ok' (OK is an example).
'about' indicates putting letters inside.
'ok' placed around 'a' is 'OAK'.
(Other definitions for oak that I've seen before include "Nose of certain wines" , "Traditional British tree" , "Common forest tree" , "Acorn-bearing tree" , "Hard durable wood of a deciduous tree" .)