Soldier's turned up to identify large tree (8)
I believe the answer is:
rifleman
'soldier's' is the definition.
(I've seen this before)
'turned up to identify large tree' is the wordplay.
'turned up' shows that the letters should be reversed in order.
'to identify' becomes 'name' ('name' can be a synonym of 'identify').
'large' becomes 'l'.
'tree' becomes 'fir' (fir is a kind of tree).
'name'+'l'+'fir'='namelfir'
'namelfir' in reverse letter order is 'RIFLEMAN'.
(Other definitions for rifleman that I've seen before include "Sniper" , "Nil frame for a member of the infantry" , "Bird" , "Soldier carrying gun" , "Soldier - crack shot?" .)