Tree, or its remains? (3)
I believe the answer is:
ash
I believe this clue is a double definition.
'tree' is the first definition.
(ash tree is a kind of tree)
'remains?' is the second definition.
(I've seen this before)
'or its' acts as a link.
(Other definitions for ash that I've seen before include "remains after forest fire?" , "Tree with pale wood" , "It no longer burns" , "Grey colour" , "Tree; fire residue" .)