A nail hammered like that in tree (9)
I believe the answer is:
ailanthus
'tree' is the definition.
(ailanthus is a kind of tree)
'a nail hammered like that' is the wordplay.
'hammered' indicates anagramming the letters (slang term for drunk).
'like that' becomes 'thus' (I've seen this before).
'nail' with letters rearranged gives 'ilan'.
'a'+'ilan'+'thus'='AILANTHUS'
'in' is the link.
(Other definitions for ailanthus that I've seen before include "ornamental tree" , "Tree of Heaven; Thai Alnus (anag.)" .)