Good to hug a tree (3)
I believe the answer is:
oak
'tree' is the definition.
(oak is a kind of tree)
'good to hug a' is the wordplay.
'good' becomes 'ok'.
'to hug' is an insertion indicator.
'ok' going around 'a' is 'OAK'.
(Other definitions for oak that I've seen before include "Hardwood tree" , "Acorn-bearing tree" , "Nose of certain wines" , "Large tree" , "Building timber" .)