Alright to take a tree (3)
I believe the answer is:
oak
'tree' is the definition.
(oak is a type of tree)
'alright to take a' is the wordplay.
'alright' becomes 'OK' (synonyms).
'to take' is an insertion indicator (inserted letters are taken in).
'ok' going around 'a' is 'OAK'.
(Other definitions for oak that I've seen before include "Acorn-bearing tree" , "Grown acorn" , "Its seed is the acorn" , "Building timber" , "From little acorns does it grow" .)