Plot left half-finished for tree (5)
I believe the answer is:
maple
'tree' is the definition.
(maple is a kind of tree)
'plot left half-finished' is the wordplay.
'plot' becomes 'map' (plot can mean to map or chart).
'half finished' suggests halving the letters.
'left' cut in half is 'le'.
'map'+'le'='MAPLE'
'for' is the link.
(Other definitions for maple that I've seen before include "Ample sort of tree" , "Cathedral city in Devon" , "Emblematic tree of Canada" , "Tree; sugar from it" , "Tree with winged seeds" .)