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