A tree found in part of London (6)
I believe the answer is:
poplar
This clue is a double definition.
'a tree' is the first definition.
(poplar tree is a kind of tree)
'part of london' is the second definition.
(district of East London)
'found in' is the link.
(Other definitions for poplar that I've seen before include "Timber tree" , "Tall tree of north temperate regions" , "The tree that quivers" , "Slender tree with quivering leaves" , "tree found mostly in the northern hemisphere" .)