Axes chop and sharpen instrument ... (9)
I believe the answer is:
xylophone
'instrument' is the definition.
(xylophone is a kind of instrument)
'axes chop and sharpen' is the wordplay.
'axes' becomes 'xy' (x axis and y axis).
'chop' becomes 'lop' (I've seen this in other clues).
'and' means one lot of letters go next to another.
'sharpen' becomes 'hone' (honing is a kind of sharpening).
'xy'+'lop'+'hone'='XYLOPHONE'
(Other definitions for xylophone that I've seen before include "Oxyphenol (anag.)" , "Percussion instrument played with mallet" , "Patrick Moore's instrument" , "Musical instrument with bars" , "Instrument with wooden bars to be struck" .)