Axes chopped up elm's woody tissue (5)
I believe the answer is:
xylem
'woody tissue' is the definition.
(I've seen this in another clue)
'axes chopped up elm's' is the wordplay.
'axes' becomes 'xy' (x axis and y axis).
'chopped up' is an anagram indicator.
'elm' anagrammed gives 'lem'.
'xy'+'lem'='XYLEM'
(Other definitions for xylem that I've seen before include "trees - it's natural for them" , "Woody part of plants" , "wood" , "Woody plant tissue" .)