Large curved structure in wood (5)
I believe the answer is:
larch
'wood' is the definition.
(I know that larch is a type of wood)
'large curved structure' is the wordplay.
'large' becomes 'L' (eg in clothes sizes).
'curved structure' becomes 'arch' (I've seen this before).
'l'+'arch'='LARCH'
'in' is the link.
(Other definitions for larch that I've seen before include "Supplier of timber" , "Deciduous conifer" , "Coniferous tree with deciduous bright green needles" , "wood" .)