Has destroyed a tree (3)
I believe the answer is:
ash
'a tree' is the definition.
(ash is a kind of tree)
'has destroyed' is the wordplay.
'destroyed' is an anagram indicator.
'has' with letters rearranged gives 'ASH'.
(Other definitions for ash that I've seen before include "End of fire" , "Get the residue" , "Remnant from fire" , "Tree with pale wood" , "Tree - effect of burning" .)