Tree in plot on base (5)
I believe the answer is:
plane
'tree' is the definition.
(plane is a type of tree)
'plot on base' is the wordplay.
'plot' becomes 'plan' (I've seen this before).
'on' is a charade indicator (letters next to each other).
'base' becomes 'e' (I've seen this in other clues).
'plan'+'e'='PLANE'
'in' is the link.
(Other definitions for plane that I've seen before include "Woodworking tool" , "Tool for smoothing wood" , "Smoother" , "Form of transport" , "that soars into the sky" .)