Tree used wild apes at the end of the garden (5)
I believe the answer is:
aspen
'tree' is the definition.
(aspen is a kind of tree)
'wild apes at the end of the garden' is the wordplay.
'wild' indicates anagramming the letters.
'at the end of' says to take the final letters.
The final letter of 'garden' is 'n'.
'apes' with letters rearranged gives 'aspe'.
'aspe'+'n'='ASPEN'
'used' acts as a link.
(Other definitions for aspen that I've seen before include "A poplar with shivering leaves" , "Type of poplar" , "One trembling" , "Tree that quivers" , "Very timid" .)