Tree line in front of bridge (5)
I believe the answer is:
larch
'tree' is the definition.
(larch tree is a kind of tree)
'line in front of bridge' is the wordplay.
'line' becomes 'l'.
'in front of' says to put letters next to each other.
'bridge' becomes 'arch' (I've seen this before).
'l'+'arch'='LARCH'
(Other definitions for larch that I've seen before include "Coniferous tree with deciduous bright green needles" , "Supplier of timber" , "Deciduous conifer" , "wood" .)