Drunken con-man in tree (8)
I believe the answer is:
cinnamon
'tree' is the definition.
(cinnamon is a kind of tree)
'drunken con-man in' is the wordplay.
'drunken' indicates an anagram.
'con'+'man'+'in'='conmanin'
'conmanin' is an anagram of 'CINNAMON'.
(Other definitions for cinnamon that I've seen before include "The spice is oddly non-manic" , "Yellowish-brown - spice" , "Spicy bark" , "Aromatic tree bark used as a spice" , "Spice from dried bark" .)