Left bow in tree (5)
I believe the answer is:
larch
'tree' is the definition.
(I know that larch is a type of Pinophyta)
'left bow' is the wordplay.
'left' becomes 'l' (common abbreviation).
'bow' becomes 'arch' (both can mean to curve).
'l'+'arch'='LARCH'
'in' acts as a link.
(Other definitions for larch that I've seen before include "Coniferous tree with deciduous bright green needles" , "Supplier of timber" , "Deciduous conifer" , "wood" .)