Catkin-bearing tree (5)
I believe the answer is:
alder
'catkin-bearing tree' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for alder that I've seen before include "One [TYPE OF TREE]" , "Tree related to the birch" , "Artificial fishing fly" , "Tree or shrub whose wood is resistant to underwater rot" , "North temperate tree with cone-like fruit" .)