Tree that gets shot in army base (5)
I believe the answer is:
alder
'tree' is the definition.
(alder is a kind of tree)
I don't understand how the remainder of the clue works.
(Other definitions for alder that I've seen before include "Tree related to the birch" , "North temperate tree with cone-like fruit" , "Artificial fishing fly" , "Water resistant wood" , "Tree with toothed leaves and cone-like fruits" .)