Around and around, circle tree (5)
I believe the answer is:
cacao
'tree' is the definition.
(cacao tree is a kind of tree)
'around and around circle' is the wordplay.
'around' becomes 'ca' (circa).
'and' means one lot of letters go next to another.
'around' becomes 'ca' (circa).
'circle' becomes 'o' (O is a circle).
'ca'+'ca'+'o'='CACAO'
(Other definitions for cacao that I've seen before include "Tropical tree, the source of chocolate" , "Plant" , "Tree supplying chocolate" , "Tree for cocoa bean" , "Tree with seeds used to make chocolate" .)